Nigel Farage said Ukip's gains in the local elections "look like a fairly permanent protest" as he arrived to cheers in Thurrock this afternoon.
Mr Farage added it was difficult to predict whether his party's surge would be more harmful to Labour or the Conservatives, as many who voted Ukip "probably hadn't voted for anybody for 20 years."
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.