Nigel Farage will use Ukip's annual conference, which opens in Doncaster today, to launch a "full frontal assault" on Labour and Ed Miliband.
For a long time Ukip was seen primarily as a threat to the Tories. But Farage sees expanding his reach into Labour's working class heartlands in the North of England as key to further electoral success.
The conference, deliberately being staged on the border of Ed Miliband's Doncaster North constituency, will see Ukip spokespeople offer "stark criticism of Labour's failings".
Among policies set to be unveiled over the next two days include plans to cut income tax from 40p to 35p for people earning up to £55,000.
Many in Labour's high command saw the rise in support for the eurosceptic party, given it was seen to damage the Conservatives in marginal seats, as a useful tool that would help put Miliband in Downing Street in 2015. However that the party now appears to be taking the threat from Ukip seriously.
There were no less than three fringe meetings in at Labour's Manchester conference dedicated to fighting Farage, all packed with worried activists and candidates. And some Labour MPs are increasingly nervous about their voters switching to Ukip. Rotherham MP Sarah Champion told BBC Radio 4's Today programme this morning that Labour was "in real difficulty". She added: "Their tanks are digging up my lawn."
Labour believes key to tackling Ukip is to paint the party as simply a turbo-charged version of the Conservative Party, or "more Tory than the Tories".
Douglas Alexander, the party's election co-ordinator, told Labour delegates that he took Ukip "very seriously" and likened its rise to that of the SNP in Scotland. "I am the last person that needs to be convinced by the threat Ukip poses. The fuel in the tank of Ukip is more anti-politics than anti Europe, they will try and establish themselves as a channel for anti-politics sentiment," he said.
On the eve of the Ukip conference's opening day, there were rumours in Westminster that the party had secured the defection of another Tory MP. However when asked many of the likely suspects denied they were about to follow Douglas Carswell and jump ship.
Carswell is expected to win the 9 October Clacton by-election he triggered when he dramatically quit the Tories. His victory would give Ukip its first ever elected MP.