The Conservatives were beaten into fifth place behind the British National Party (BNP), Respect, and the Liberal Democrats came eighth.
The result comes days after a row erupted in Rotherham when it was revealed that social services had removed three children were removed from the care of their foster parents due to their membership of UKIP.
Nigel Farage, the UKIP leader, said: “Whichever way you look at it, UKIP is on the rise.”
He admitted that the row over the foster children “helped”, saying that it “put the focus on UKIP and on the other policies that we stand for as well”.
Another byelection in Middlesbrough was won by Labour’s Andy McDonald, who won a share of over 60 per cent.
He said the result sent the message to the Coalition that “you don’t speak for us” and promised to speak up for working families.
Ukip’s Richard Elvin came second with just under 12%.