The UK Independence Party claimed that they have displaced the Liberal Democrats as the third force in British politics after finishing second in two by-elections and third in another.
All three seats, Rotherham, Middlesbrough and Croydon North, were held by Labour.
UKIP recorded its best ever by-election result in Rotherham where their candidate secured 21.8% of the vote.
The coalition suffered a difficult night, with the Conservatives slumping to fourth in Middlesbrough and fifth in Rotherham.
The Liberal Democrats finished fourth and lost their deposit in Croydon and fell to eighth place in Rotherham, falling behind Labour, UKIP, the British National Party, Respect, the Conservatives, the English Democrats and an Independent.
UKIP leader Nigel Farage said the results marked "big progress" for his party.
ITV News Political correspondent Libby Wiener reports: