Rotherham, where the scandal erupted, was held by Labour, where Sarah Champion won 9,866 votes. The seat was vacated after Denis MacShane quit over his expense claims.
But Ukip’s Jane Collins took 4,648 votes, nearly 22 per cent of those cast, with the Conservatives beaten into fifth place behind the British National Party (BNP) and Respect, and the Liberal Democrats eighth.
Tory candidate Simon Wilson only just held onto his deposit while Michael Beckett, for the Lib Dems, lost his, trailing behind the English Democrats and an independent.
With just 451 votes, Mr Beckett was just 190 votes ahead of the Trade Unionist and Socialist Coalition.
Ukip’s performance was boosted by a row over foster children being taken away from a couple because they were members of the party, in a scandal first exposed by this newspaper.