Ed Miliband promised to return to Bradford West in the coming weeks to try to understand how his party was roundly defeated in what was previously considered a safe seat.
Respect candidate George Galloway beat the Labour candidate by over 10,000 votes last night, in the first by-election defeat of a main opposition party since the Conservatives lost Romsey to the Lib Dems in 2000.
“It was an incredibly disappointing result for Labour in Bradford West and I am determined that we learn lessons of what happened," Ed Miliband said.
“I'm going to lead that. I'm going to be going back to the constituency in the coming weeks to talk to people there about why this result happened.
“Clearly there were local factors, but I also say only four out of ten people voted for the three mainstream political parties. We've got to understand the reasons why that happened in Bradford."
The defeat – and worst of all its scale – is a massive humiliation for Labour and a shock to the system for political journalists, many of whom had barely paid attention to the race because it was considered so predictable.
"Not in half a century has an opposition come back from such an appalling result to win a majority at the next general election," a Conservative party spokesperson said.
"This tells you everything you need to know about Ed Miliband's weak leadership.
"If Labour can't win one of their safe seats in these tough economic times and in a tough week for the government, how can they win anywhere?"
The victory means Mr Galloway returns to the Commons for the third time in a colourful political career.