By William Schomberg and Georgina Prodhan
LONDON (Reuters) - British Prime Minister Theresa May's Conservative Party is on course to win Thursday's national election comfortably, an opinion poll suggested on Wednesday, the first of several last-minute surveys ahead of polling day.
Polling firm ICM, which has tended to give the Conservatives bigger leads than most other polling firms, said May's lead increased by one percentage point to 12 points.
Support for the Conservatives stood at 46 percent, up a point from ICM's previous poll published on Monday. Support for Labour was unchanged at 34 percent, ICM said in a preliminary poll set to be finalised later on Wednesday.
That kind of lead would give May a majority of 96 seats in parliament, up sharply from the working majority of 17 that the Conservatives had in the previous parliament.
Such a majority would vindicate May's decision to call an election less than a year after she became prime minister in the political turmoil that followed Britain's vote to leave the European Union.
May called the election in April, saying she wanted to go into the Brexit negotiations with a position of strength.
The ICM online poll of 1,532 adults was conducted between June 6 and 7, after a deadly attack in London carried out by Islamist militants on June 3.
Five other opinion polls are expected to be published later on Wednesday, including one by Survation which estimated the Conservatives' lead stood at just one percentage point in its last two polls.
There have been big differences too in estimates of how many seats the Conservatives are likely to win. Polling firm YouGov estimated earlier on Wednesday that the party would fall more than 20 seats short of a majority. Other models have predicted it will increase its majority.
The wide range of estimates of support for the two main political parties has added to scepticism among many critics of polling who point to how the industry largely failed to accurately predict the outcome of the 2015 election and last year's referendum vote to exit the European Union.
However, until recently the polls have largely shown a steady narrowing of the lead of May's Conservatives for much of the past three weeks following the publication of the parties' election policy pledges.
But a poll published by Opinium on Monday, the first by a major firm that was conducted in its entirety after the attack in London, showed the Conservatives increasing their lead to seven points.
(Writing by William Schomberg; Editing by Gareth Jones)