Ukip's Paul Nuttall said he was delighted his party were beginning to take votes from Labour, as well as the Tories.
Appearing on Good Morning Britain after a triumphant night, he said the huge gains the party made in council elections were proof voters were disenchanted with Westminster politics.
UKIP's successes in the local elections have raised the possibility of them winning a Westminster seat at the general election.
A year ahead of the general election, Ed Miliband's party is seeing only patchy support in areas it should expect to gain ground.
UKIP are likely to make Rotherham a key target for 2015 after a storming result in the local elections.