I went to the North West of England to talk to Labour campaigners about the shock of the defeat and their view on the way forward.
First stop, Bury in Greater Manchester.
The former mill town is known for its "world famous" market which attracts bus and coach tours from all over the North West - and drew in a fair few politicians for photo shoots during the general election campaign.
You can get good honest northern grub there - pies, black puddings and Lancashire cheese (pictured below) - and while you might think this classic industrial town would be a Labour stronghold, in fact it's been a battleground between Labour and the Conservatives for decades.
Not winning the parliamentary seat of Bury North, which contains the town centre, was a huge disappointment for Labour on 8 May.
The defeated Labour candidate, James Frith, a small business owner, said:  "It was devastating, in every sense, from a national point of view but also because of the sheer toil that we put in.
"We lost by 378 votes. We actually bucked the national trend in Bury North but at the count it just wasn't the night to win it."
Overall in the north west of England, Labour increased its share of the vote by just over 5% but the loss of a key marginal, Bolton West, and the failure to win target seats such as Bury North and Morecambe and Lunesdale were local signs of a wider story.
"The more you start to analyse the results, the bleaker it looks for Labour," says Prof Andrew Russell, head of politics at the University of Manchester.
"It's still useful to look at the general election result not really as a national contest but as a series of geographies of the vote. There were lots of battles where you thought the ground war would matter.
"What is remarkable is that although there were some successes for Labour in some of those ground battles, the overwhelming story is of unexpectedly bad results."
So what went wrong? For one thing, says Prof Russell, the Conservatives' campaign strategy was more sophisticated, and not just in the marginals of the north west of England.
"An electoral strategy that picks off the particular voters that might swing the vote in a particular context was the secret of the ground war and the Conservatives were much better at targeting voters with complex stories.
"So they would be appealing to Lib Dem waverers in some seats, saying if you vote Lib Dem that might let in Labour and the SNP. In other seats, they were happy for UKIP to take votes off Labour and come up on the blind side. It was a very complex picture."
The former MP Julie Hilling is still recovering from the shock of losing her seat of Bolton West to the Conservatives by 800 votes.  I caught up with her in Westminster when she returned to pack up her office and her flat.
She said two groups of her former constituents had deserted Labour on election day.
"We didn't manage to convince the white working class who are feeling very disaffected that we had the answers for them and also we didn't convince the aspirational group who were frightened of turning back to Labour."
According to James Frith in Bury North, Ed Miliband's leadership and Labour's lack of credibility on the economy were big factors in putting voters off.
Mike Tong, who worked on James Frith's campaign, said views on the campaign trail backed this up.
"On the doorstep a lot of people didn't want to vote Conservative but they didn't trust Labour in government and that ambivalence was a big issue for us. I think on the day, they drifted towards the Conservatives."
Shoppers at Bury market explained Labour's failings with Northern bluntness.
"When Labour was in power, they bloody broke the country," said one.
"I was brought up in a Labour household but some of the things they did, like giving benefits like they did, was too much," said another.
Several former Labour supporters told me they'd voted for UKIP with one woman vowing to "continue to vote for UKIP because they're more in tune with what people want".
And I found little enthusiasm for Ed Miliband and his style of leadership.
" A bit odd," said one.
"He just doesn't come over as prime minister type," was the view of another.
So how can voters like these be tempted back to Labour? Prof Russell says the party can start by having a no-holds-barred debate about its future.
"One of the things that looked like Ed Miliband's greatest asset was that he had held the party together, that the party had not done what it had done in 1979 and 1951 which was to tear itself apart about the future of social democracy or socialism and the existential crisis over what Labour was for.
"But if they still go down to the sort of defeat that Labour would have gone down to anyway, and it has just delayed the existential crisis, that now looks like a mistake. Labour now needs to solve the problem of what it is for."
Morecambe and Lunesdale was another North West seat Labour failed to gain; in fact the party's vote fell by 4.6%, with many Labour supporters clearly defecting to UKIP.
The defeated candidate, Amina Lone, who described herself as "battered and bruised" told me Labour needed to listen to UKIP voters rather than dismissing their concerns, especially about immigration, as racist.
"These people are fed up. They are significantly disillusioned with political parties and especially with Labour as they're traditional Labour voters, " she said.
"They are there for us to listen to. When I had conversations with people and talked to them about their concerns over the community changing, they re-engaged. We have to have a longer term strategy with these people."
As Labour debates its future, the party is also in search of a new leader, with nominations closing on 15 June.
The defeated candidate in Bury North, James Frith, hasn't decided who to back yet and is a little uneasy about the contest.
"I am concerned by how narrow a field it is and also by a tendency for the party to have a coronation," he said.
"I am not interested in coronations. The strongest leader is the person that immediately wants to speak to the country and not consolidate their position with the party. Frankly we've had far too much of consolidating with the party in our attempts to get into government."
According to Prof Russell, the new leader has a mountain to climb if the party is to stand any chance of forming the next government.
"Labour have had 15 to 20 years of the electoral system basically working in their favour but now it has flipped and it is now working against them. They would need a pretty much unprecedented swing from the Conservatives to Labour to get back with a majority of one.
"Add to that the regional divide, the fact that there are fewer marginal seats next time round, and the collapse of the Lib Dems in the south east and south west of England and the Tories look safer than most parties with a slim majority would have looked."
The defeated candidate in Morecambe, Amina Lone, has a succinct but by no means simple, summary of the task ahead for Labour.
"Get a new leader, get a vision. There's a huge chunk of people who can buy into Labour's vision but we have to decide what it is before we can sell it to anybody else."
Listen to the report on the Westminster Hour here.
Labour is still reeling from its general election disaster, which reduced the party to its lowest number of MPs since 1987, left members battered and bruised and started the search for a new leader.