LONDON British Prime Minister Theresa May's lead increased to 15 percentage points in a poll conducted over a week ago and published on Wednesday, but is likely to narrow in an upcoming poll, market research company Panelbase said on Wednesday.
Survey work for Wednesday's poll took place both before and after last week's suicide bomb attack in Manchester, and its publication was delayed.
The May 19-23 poll showed the Conservatives with 48 percent share of those certain to vote in the June 8 election versus 47 percent in a May 15 poll. The main opposition Labour Party took a 33 percent share, unchanged versus the earlier poll.
However, the previous survey used a different methodology to Wednesday's poll, and included those who were not certain to vote. If Wednesday's poll had used the previous poll's methodology, it would have shown the Conservatives' opinion poll lead narrowing by 6 percentage points, Panelbase said.
"We will be releasing another poll in the next day or two and early indications are that it will show a further narrowing of the Con-Lab gap," Panelbase said.
Other polls carried out since the May 22 Manchester attack have shown May's lead over the opposition Labour Party shrink, suggesting she might not win the landslide predicted just a month ago.
(Reporting by Elisabeth O'Leary and Andy Bruce, editing by David Milliken)