British Prime Minister David Cameron's Conservatives on Friday took the lead in a YouGov opinion poll for the first time since March 2012, following his party conference speech.

Cameron's address on Wednesday promised tax cuts for 30 million workers if the Conservatives win the May 2015 general election and his speech was largely seen as a pitch to be returned to office.

The poll put the centre-right Conservatives on 35 percent, with the opposition centre-left Labour Party, led by Ed Miliband, on 34 percent.

The populist United Kingdom Independence Party (UKIP) was on 14 percent and the centrist Liberal Democrats, the junior partner in the coalition government, on six percent.

If replicated at the general election, with an even swing, such figures would, due to the formulation of Britain's constituencies, likely still leave Labour comfortably the biggest party in parliament but slightly short of a majority.

The survey found people expect their finances to suffer less under a Conservative government, but believe they will be poorer in five years' time irrespective of who wins.

YouGov president Peter Kellner said the big polling issues ahead of the election remained unresolved.

"Can the Tories turn their big lead over Labour on the economy into extra votes as the election approaches? Can Miliband persuade floating voters that he is up to the job of prime minister?" he asked.

He also said it was unclear whether UKIP could hang on to the mainly Conservative voters it had won in the past two years, if the Liberals could revive their "terrible fortunes" and whether the Scottish nationalists could overrun Labour strongholds in Scotland.

YouGov surveyed 2,133 British adults on Wednesday and Thursday.