The Conservative Party was humiliated in three by-election seats in Croydon North, Middlesbrough, and Rotherham.
While Labour candidates won the three parliamentary seats, the UK Independence Party (Ukip) managed to secure second place in Middlesbrough and Rotherham - its best-ever electoral performance.
In the Rotherham by-election, which was precipitated by the resignation of former Labour MP Denis MacShane over parliamentary expenses abuse, the Tories were pushed into fifth place behind the British National Party and Respect. Although the Conservative contender Simon Wilson managed to retain his deposit, the Lib Dem candidate Michael Beckett lost his after finishing eighth.
The Rotherham and Middlesbrough seats were won by Sarah Champion and Andy McDonald respectively, while Steve Reed came first in Croydon North.
"Cameron's Tories have shown what they think of Rotherham, and today this result tells David Cameron what Rotherham thinks of the Tories," said Champion soon after the election results, adding: "I've never stood for election before but when I see the damage David Cameron is doing to Rotherham I cannot stand and watch."
Ukip's strong performance in Rotherham comes less than a week after the town's council took three immigrant foster children away from a local couple because they supported the right-of-centre party, which advocates tougher immigration controls for Britain.
Ukip leader Nigel Farage said it was a "big night" for Ukip, adding: "Our previous best ever by-election result a fortnight ago was 14.3% and this one is comfortably over 20%. Whichever way you look at it, UKIP is on the rise."