Ed Miliband has kick-started Labour's final conference before the general election with a pledge to hike the minimum wage to at least £8.

The party leader said the rise over the next parliament - from the £6.50 level it will hit next month - was needed to stop ordinary workers being left behind.

The increase would add around £3,000 a year to the pay packets of those earning the minimum wage.

The announcement by Mr Miliband, in interviews with the Sunday Mirror and Observer, is thought to be the first of a series of interventions during the gathering in Manchester to focus on stagnating living standards under the coalition.

The Labour leader has already declared that his focus is now fully back on the election contest after the decisive No vote in the Scottish independence referendum.

However, he is likely to face more pressure over David Cameron's demand for a solution to the so-called West Lothian Question - the ability of Scots MPs to vote on measures that only affect England.

The Prime Minister has sought to tether reforms at Westminster with the extra devolution promised to Scotland during the referendum campaign.

But Labour, which has around 40 MPs north of the border, insists the issues should be addressed separately.

It has called for a constitutional convention to consider the English situation over a number of years.

Speaking to the Sunday Mirror, Mr Miliband said: "Too many working people have made big sacrifices but in this recovery they're not seeing the rewards for their hard work because, under the Tories' failing plan, the recovery is benefiting a privileged few far more than most families.

"One in five of the men and women employed in Britain today do the hours, make their contribution, but find themselves on low pay.

"But if you work hard, you should be able to bring up your family with dignity."

Mr Miliband added: "This week Labour's Plan for Britain's Future will show how we can change and how we can become a country that rewards hard work once again. Because Labour is the party of hard work, fairly paid."

The planned increase, which would affect around 1.4 million jobs, would be introduced in annual stages by the Low Pay Commission before October 2019.

The promised rate is said to be similar to that in force in Australia and EU countries such as Belgium and Germany, but still lower than in France and New Zealand.

Mr Miliband attacked Mr Cameron for calling for "English votes for English laws" immediately after the Scottish referendum result.

"He didn't talk to me before he made his announcement. I don't think he rose to the moment," he said. "Constitutional change has got to be done by the people, not in the corridors of Westminster."

Shadow education secretary Tristram Hunt and shadow communities secretary Hilary Benn are among those addressing Labour activists today.

Earlier yesterday shadow equalities minister Gloria De Piero announced proposals to force large firms to publish the average salary of men and women across every level of their organisation as part of efforts to deliver equal pay.

Meanwhile, Deputy Leader Harriet Harman delivered an impassioned defence of all-women shortlists, insisting no other measures were effective in promoting gender balance in parliament.

The party also revealed plans to set up New Homes Corporations to boost the number of properties being built.

The corporations could take responsibility for areas prioritised for development, and set out the timetable over which construction will take place.

Conservatives said that the Government had already delivered the first real-terms rise in the minimum wage since the 2008/09 recession, with the main rate due to increase to £6.50 an hour on October 1, after Chancellor George Osborne gave evidence to the Low Pay Commission that the economy could afford an above-inflation hike.

The minimum wage has fallen by 22p an hour in real terms since the second quarter of 2008, costing a worker on 40 hours a week £455 a year, said a source.

Culture Secretary Sajid Javid said: "The Conservatives are already delivering the first above-inflation minimum wage rise since Labour's great recession began, something we can only afford because our long-term economic plan is working.

"Nobody will take any lectures from Labour on helping people on low pay. By crashing the economy, Labour made everyone poorer. And they haven't learnt their lesson. Ed Miliband would make people worse off with the same failed policies that got us into a mess in the first place - more wasteful spending, more borrowing and higher taxes.

"Only by sticking to our plan will we raise hard-working taxpayers' living standards and secure a better future for Britain, and for our children and grandchildren."

John Longworth, director general of the British Chambers of Commerce said: "There is no doubt that the widening pay gap and a lack of social mobility is detrimental to the UK economy. As the economy continues to improve, businesses agree that the minimum wage must rise. In recent polling, 60% of Chamber members recommended an increase in line with current inflation, and 14% favoured an above-inflation increase.

"However, businesses are in favour of an evidence based approach to the minimum wage rather than political parties using it to gain support from voters. The Government should not intervene in such matters, unless there is market failure.

"A range of existing mechanisms, such as the Low Pay Commission and Living Wage Commission, are already in place to determine the optimal resolution for workers, businesses and long term economic growth.

"Politicians should instead focus on implementing policies to raise productivity and improve skills in the workplace - which are the keys to higher wages for all in the future."

Shadow business secretary Chuka Umunna insisted workers would be better off as a result of the increased minimum wage, but was unable to say how much of the money they would keep after the effects of increased income tax and the withdrawal of benefits were taken into account.

He told BBC1's Sunday Politics the policy would "pay for itself" because of the increased tax take and reduction in the welfare bill.

"The policy absolutely pays for itself. The way we have looked at this, we have actually looked at the Government's own figures because of course if people are earning more, they will therefore be paying more in income tax, they will be receiving less in benefits, we will have to be paying out less in tax credits.

"So we are absolutely confident that this will pay for itself."

Asked how much of the increased wage workers would be able to keep he said: "We are confident, we have done the modelling on this. I can't give you an exact figure."

Put to him that up to 65% of the money could be lost in tax and withdrawn benefits, Mr Umunna said he did not accept that figure.

He acknowledged he could not provide an alternative, saying: "I don't have any in my head which I can give you right now."

But he added: "We are confident that people will have more in their pocket and they will be better off with the change that we are proposing. Of course the other thing that we are also seeking to do is to incentivise employers to pay a living wage as well."

John Allan, chairman of the Federation of Small Businesses, said: "The FSB has always supported the minimum wage but we are increasingly concerned that it's becoming a political football. Giving businesses a longer term view of what the minimum wage will look like in future years is an idea we support, but the decision on what the rate is should be made only after consultation with the Low Pay Commission. This proposal does the opposite.

"Our concern is that setting rates according to political need means that the impact of rises on employment, inflation and growth will not be fully explored. Sectors such as retail and social care are run on very fine margins, and will struggle with substantial increases to the minimum wage rate that fail to take wider economic conditions into account.

"The FSB therefore believes the rate should continue to be based on an independent LPC's recommendations, and that future rates should be determined following careful consultation with the Office for Budget Responsibility, business groups and workers' representatives to ensure the decision takes into account the full economic picture."

Julia Unwin, chief executive of the Joseph Rowntree Foundation, said: "Of course we welcome the promise made by Ed Miliband to raise the minimum wage. It is good to see the issue finally getting the attention it deserves. However, people are going to need to see much more from Labour if they are to be convinced that the party can really make in-roads into ending poverty.

"It is about more than just pay, policies are needed to tackle the high cost of childcare and housing, a dearth of quality part-time jobs and better progression for low-paid workers.

"Addressing low pay is an important first step in reducing the UK's in-work poverty problem, though what we need to see political parties deliver at party conference season is a comprehensive strategy to reduce poverty across the UK."

TUC general secretary Frances O'Grady said: "Raising the minimum wage and putting more money into the hands of low-paid workers won't just be welcomed by hard-pressed families, it will also be good news for local economies who will benefit from a boost in workers' spending power.

"The predictable scaremongering from business about the impact of a rising minimum wage on jobs should be ignored. They said the same in the 1990s before the minimum wage was introduced. They were wrong then and they are wrong again now.

"After years of falling real pay we need a range of policies to ensure fairer pay from board level to the shop floor. The TUC believes Britain needs a pay rise - only then will the recovery start to feel real for people in work."