Prime Minister Theresa May arrives at the Ealing Conservative Association in London, Britain May 20, 2017. REUTERS/Toby Melville

LONDON (Reuters) - Prime Minister Theresa May’s Conservatives’ lead over the opposition Labour Party halved to 9 percent in a Survation telephone poll published on Monday, adding to signs that the election race is tightening ahead of the June 8 vote.

The poll put the Conservatives on 43 percent, down 5 percentage points from a May 15 poll, with Labour at 34 percent, a reported rise of 5 points due to rounding. The research was conducted on May 19 and 20 after the release of the Conservative and Labour manifestos.

Although May’s center-right party remains well in front of their leftist rivals, several recent polls showing a narrowing gap suggest that expectations of a landslide victory for the Conservatives may need to be lowered.

Senior Conservative ministers on Sunday defended proposals to reduce state support offered to elderly voters despite concerns that it could undermine support among aging, wealthy homeowners - a core source of Conservative votes.

The poll showed that respondents were more likely to say that Labour, rather than the Conservatives, had the best policies for older people and pensioners, as well as young people and the state-funded healthcare service. The Conservatives were seen as stronger on the economy and Brexit.

May called the snap election to increase the 17-seat working majority she had in parliament and secure a public mandate for her negotiating strategy as Britain prepares to begin talks on leaving the European Union.

At the time the election was called, poll leads in excess of 20 percent had suggested she could deliver the largest Conservative victory since Margaret Thatcher won a 144-seat majority in 1983.

Monday’s Survation poll showed the Liberal Democrats and the UK Independence Party (UKIP) were unchanged at 8 percent and 4 percent respectively.