British Prime Minister David Cameron's Conservative Party is one point ahead of the opposition Labour Party before Thursday's election, according to a poll carried out by research firm Opinium and published on Wednesday.

The poll put Cameron's party on 35 per cent, unchanged from a previous Opinium poll, and Labour also unchanged at 34 per cent.

Support for anti-European Union UKIP fell one point to 12 per cent, the Liberal Democrats were unchanged at 8 per cent and the Greens rose one point to 6 per cent, Opinium said.