The Conservatives Party has lost a seat to Labour at a by-election for the first time in 15-years, after being heavily beaten in Corby.
Labour's Andy Sawford handily won the seat vacated by Louise Mensch with 17,267 votes, a majority of 7,791 over Christine Emmett, the Tory candidate who won 9,476 votes.
Speaking after his victory was announced, Sawford, the son of former Kettering MP Phil Sawford, said he was "incredibly proud" to be elected to parliament.
"This result is an historic gain for today's one nation Labour Party. today Middle England has spoken. They have sent a very clear message to David Cameron.
He added: "The road to Downing Street runs through Corby."
The Conservatives expected to lose the seat, however the size of the vote for Ukip, which came third with 5,108 votes, spells trouble for David Cameron who is under pressure from eurosceptic backbenchers to deal with the threat by promising a referendum on Europe.
The Tories also fared badly in one of yesterday's other by-elections won by Labour, Manchester Central, where they only scraped into third place, with 754 votes to Ukip's 749.
The Corby by-election was called after sitting MP Mensch decided to quit parliament after just two years in order to move her family to New York.
On Thursday evening after polls closed the ex-MP predicted Labour would win and accepted the blame. "Election result will not be a verdict on either Christine, or the Conservatives, but only on the decision I took to step down mid-term," she said.
She added: "Though I had to resign to unite our family, there was large & entirely understandable local anger. I wish I had been able to see out my term."
Responding to the Corby result, David Cameron said: "It's a classic mid-term result and obviously made difficult by the fact that the Conservative MP left the seat in question.
And Conservative Party chairman Grant Shapps admitted that Mensch "going off to live in America wasn't an ideal backdrop" for the election.
The victory in Corby is a good sign for Ed Miliband and Labour, as in every general election since 1983 Corby has voted for the party that has ended up in government.
The Corby result was embarrassing for Nick Clegg's Lib Dems however, who forced a limited recount in a last minute effort to avoid losing their deposit. Lib Dem candidate Jill Hope came in fourth place with 1,170 votes.
Ukip leader Nigel Farage said the Corby result was the party's best ever in a parliamentary by-election and showed it had become "the third force in British politics".
"This is a great result for Ukip," he said.
"Along with the other results coming in from around the country today - including the 31% we scored in a council by-election in Manchester - it confirms that we are now established as the third force in British politics."