My dream to save the poor Valerie Amos was the first black woman in the cabinet and first black leader of the Lords. Her next challenge? She could be faced with halving world poverty in just 10 years.

"But just about all I've done in my working life has been good training for whatever came next."

So far that training has brought two historic distinctions. Baroness Amos, who was born in Guyana in 1954, is the first black woman to become a member of the cabinet and the first black leader of the House of Lords. Soon, however, she may be leaving the British political stage for the further elevation of a United Nations post. The prime minister, a long-time admirer of her powers of persuasion and tireless capacity to absorb a complicated brief, has nominated her to head the UN development programme which is charged with halving world poverty by 2015. Our conversation takes place just before that Downing Street announcement and protocol demands that Amos doesn't comment on her candidacy, one among several submitted by other countries. Secretary-general Kofi Annan is likely to announce the chosen appointee by late spring.

In the meantime, it's business as usual, although there is scarcely anything usual about Amos's hefty workload and the tightrope she walks between the Commons and the Lords, a tightrope that, in fact, became a bit of a tug of war last week as the government and the upper chamber pulled in opposite directions over the proposed antiterrorism bill. Indeed, it might seem that in moving to the Lords from those turbulent local government days in the 1980s and fractious tussles at the EOC, Amos has simply swopped one awkward squad for another. But she doesn't see her fellow peers as trouble-makers, even though much of her present job demands that she reform them.

"There is an expectation that I uphold what the government is attempting to do, but there is also an expectation that if the House of Lords gets into some kind of fight about its role in holding the government to account, then I will stand up for the Lords."

Strikingly handsome and elegant, Amos possesses the kind of informal charm that can take the sting out of hostile encounters and suggests diplomacy comes with her DNA. When she was nine she arrived in Britain with her parents, brother and sister, and the culture shock could not have been greater:

instead of the tropical lushness of Guyana the location now was white, suburban Kent. Yet she has recalled that hers was a mostly harmonious childhood, although there was one occasion when a neighbour campaigned unsuccessfully to stop her family buying a house in the street.

"My father initially came to study but, as he was a teacher anyway, he started teaching here."

That background spurred Amos to succeed and at her girls' grammar school in Bexleyheath she excelled academically and in sport. That early experience has also finelytuned her to the complexities of asylum and immigration, not least because draconian rules surrounding the issue would previously have locked the door against British immigrants like herself.

"A country has to be absolutely clear about what it means. I recognise that people want to get the best for their family and will wish to move to countries which will give them that opportunity.

So, we have to find ways of managing that." Today's tidal shifts of humanity are the reality of a changing world and, while Amos has said that governments cannot take in all-comers, she doesn't accept the argument that asylumseekers enter Britain to exploit the benefits system.

History has proved their contribution is valuable and Amos has warned both Labour and the Conservatives against allowing warring words over the issue to dominate the general election campaign. "That would have the potential to destabilise communities which have found ways of living and working together. I certainly don't want local campaigning on immigration and asylum being code for 'no more blacks'."

Amos prefers the phrase multiheritage rather than multicultural as a definition of society, and she urges that we should encourage children to understand that our history as a nation has emerged from all sorts of different places. "It all has importance. We don't need to be ashamed of where we have come from." She herself can trace her ancestry to the Ashanti kingdoms of west Africa.

Those who have worked with Amos always refer to her sense of balance in debate. "While others around her took extreme positions, " recalls one contemporary from the Lambeth days, "Valerie exercised restraint, never getting a word out of place." But does she feel patronised when commentators describe her as a safe pair of hands? "Well, I do believe strongly in collective responsibility. That doesn't mean that if I disagree with something I won't say so, but once the cabinet has made its decision then I stick with it. Yet somehow this way of thinking has become discredited."

On Lords reform Amos knows her own mind: the prime minister may favour an appointed upper chamber but she believes an elected arrangement based on regional representation would be the better option. "That's always been my position and what I've always voted for. I also think there is absolutely no reason why we shouldn't say that peerages confer an honour on people who have achieved X, Y and Z in society but that in itself doesn't mean they've a right to vote in the second chamber."

If progress towards a final solution is tortuous, Amos maintains the Lords has already changed a great deal since 1997. "The number of women has doubled.

There are more ethnic minorities and, of course, most of the hereditaries have gone."As a result, the culture of the place, she says, has assumed increased legitimacy. "In its relationship with the Commons, the House f lexes its muscles much more than in the past. There is a real sense that it sees itself as the chamber that scrutinises legislation in detail and says to government, 'Are you sure you've got this right?

We need to ask you to think again'."

Tony Blair first encountered Amos when he was shadow employment secretary and she, as head of the EOC, worked with him on a series of fairness-at-work campaigns. When New Labour came to power, hers was among the first names destined for a peerage and her rise to prominence has been spectacular: government whip, spokeswoman for social security, women's issues, international development and the foreign office. But her track record in foreign affairs and on Africa in particular was well established before she moved to international development after Clare Short's emotional departure on resigning from the cabinet over Iraq. In fact, Amos's overseas concern dates from her student days at Warwick University when she took part in demonstrations against South Africa's apartheid regime and against oppression in Angola, Zimbabwe and Mozambique.

If her charm offensive failed in its mission to gain Britain the backing of wavering African states on Iraq, her doggedness and sensitivity to the continent's concerns won the admiration of many. "No assumptions were made that we somehow would railroad smaller countries into what we thought ought to be done. That wasn't the basis of my engagement but, although the outcome was disappointing, it was actually a really interesting time."

Diplomacy, though, hasn't deterred her from tearing a strip off President Robert Mugabe. In 2003, during a speech in South Africa in which Amos listed his outrages against human rights, she dismissed Mugabe's criticisms that Britain was acting as a colonial power. "Those days are gone, " she said. "The fact that it is me standing here as a British minister, a descendant of those colonised, is demonstration of this." But Amos is careful not to demonise. "A government that will deprive its people of food for political purposes - well, you have to speak out against that. But I also believe we have to acknowledge our own history on Zimbabwe. Other African countries feel very strongly that when Zimbabwe was going through apartheid and land was being stolen, nobody - or only a few - stood up in parliament here and made the kind of noise heard now in respect of the Mugabe issue."

But, as a result of the tsunami appeal, charity donations to Africa are down by 20-per cent. How difficult will it be to maintain the momentum of the government's commitment to the continent? "The commitment is not a one-off. The spotlight is on the issue this year because Britain is chairing the G8, so there is political impetus. But, given Africa's scale of need, this has to be an ongoing commitment for long-term sustainability. And the (public's) extraordinary response to the tsunami yet again belies those who say we're suffering from compassion fatigue."

Amos retains strong emotional links with the Caribbean, which she describes as giving added value to her Britishness. "I see that as positive, another dimension of who I am. It's not something pulling me in different directions." But what has the speed of her rise to prominence taught her about herself? "That I'm resilient and have an ability to make connections and form coalitions around diverse issues. But I don't have to be the centre of things. I'm delighted just to put people together so that they'll be the ones to make action happen."

If she does go to the UN, Valerie Amos will have landed one of the toughest tasks on the planet:

tackling the horrendous misfortunes inf licted on the poor, not just by natural disasters and disease but by war, corruption and greed. Against that, the battles she might have with any remaining, uppity old devils in the Lords will seem as decorous as taking tea on the terrace.

CV: Baroness Amos of Brondesbury

Born: Guyana, March 1954,

Status: Unmarried.

Education: Townley Grammar School for Girls, Bexleyheath; Warwick University.

Career: Classic passage from local government left-winger to New Labour moderate.

Highs: "Being the first black woman in the cabinet, and coming to the House of Lords and watching the pride of my parents on that day."

Lows: "Gosh, there aren't any obvious lows."