BRITAIN will need to show the same spirit of national mission and determination as people demonstrated at the end of the Second World War if it is to rebuild itself and avoid a decade-long slump, Ed Miliband will say today.

At a public question-and-answer session on the eve of Labour's conference in Manchester, the UK party leader will insist after two-and-a-half years of a failed Coalition Government people are facing a crisis in living standards, which is "profound, prolonged and painful".

Mr Miliband will say: "This is an economic emergency. We are at risk of a decade-long decline in living standards. For millions of families, the prospects feel bleaker now than for 50 years, since the Second World War.

"And we will need the same spirit to overcome this crisis as Britain showed then and in our gravest moments through history: The same spirit, the same determination, the same sense of national mission that there was as our parents and grandparents rebuilt Britain after the Second World War.

"The task of our generation is different than it was then but it has this in common: We need to rebuild."

He will stress whoever wins the next election face a huge deficit. If the Opposition wins, it will have to make difficult decisions and will not be able to reverse all the Coalition cuts.

"We will take decisions about priorities like putting jobs ahead of pay rises. But don't believe those who say all politicians are the same because our decisions will be different."

He will say Labour in government would put the interests of millions of working people ahead of tax cuts for millionaires, it would tax bankers' bonuses to get young people into jobs and begin work on long-term infrastructure projects – the so-called Plan B.

Mr Miliband will add: "Don't believe those who say there is nothing that can be done to ease people's struggles right now because when times are tough, government should be on your side. That is how we are going to bring real change to this country. That is the start of how we can rebuild Britain."

The Labour faithful gather in Manchester boosted by a poll, which shows the party with a record lead of 16 points.

The TNS BMRB snapshot of 1150 people puts Labour on 44%, Conservatives on 28% and LibDems on just 8%. This is the first time the Tories have fallen below 30% since the 2010 General Election. The poll shows there has been a shift of disaffected LibDem voters to Labour.

Of those supporting Mr Miliband and his colleagues, 35% say they voted Liberal Democrat the last time round. Furthermore, some 22% now supporting Labour say they did not vote at all in the 2010 election.

However, when Mr Miliband's competence is compared to David Cameron's, the Prime Minister still has a lead, albeit smaller than before.

In October 2011, when asked how much confidence people had in the party leaders solving the nation's problems, 41% backed Mr Cameron and 25% Mr Miliband; a gap of 16%. Asked the same question this month and the respective replies were 35% and 29%; a gap of six points.

Margaret Curran, Shadow Scottish Secretary, told The Herald this week's conference would be a pivotal moment for Mr Miliband, saying it will mark the point at which the public regards him not as just a leader of the Opposition, but as a prospective prime minister.

She said: "Every time people have criticised Ed, saying he hasn't done this or he hasn't done that or he's too weak, he has always surprised people, he's always come through. We will see at this conference that Ed will demonstrate himself as a clear leader."