British Prime Minister David Cameron's Conservative Party took a one-point lead over the opposition Labour Party, according to a YouGov opinion poll for the Sun newspaper published on Sunday.
The poll showed the Conservatives with 34 percent versus Labour tallying 33 percent, polling company YouGov said.
Britons will vote on May 7 in what is expected to be the tightest election in decades.
The two main parties have been neck-and-neck in most opinion polls since the start of the year, with neither establishing a sustained lead that exceeded the three-point margin of error.
Opinion polls have shown that neither of the two main parties was likely to win an overall majority in the 650-seat Parliament.