LONDON (Reuters) - British Prime Minister Theresa May’s Conservative Party has opened up the biggest lead on record for polls conducted by research firm ICM, suggesting it remains on course for a sweeping win in a national election in a month’s time.

Britain's Prime Minister Theresa May addresses Conservative parliamentary candidates for London and the south east at the Dhamecha Lohana Centre in Harrow, north west London, May 8, 2017.REUTERS/Stefan Rousseau/Pool

An ICM poll published on Monday, which was conducted immediately after the Conservatives scored big wins in local elections last week, gave May’s party a 22-point lead over the opposition Labour Party ahead of the June 8 national election.

May caught her political rivals and investors unawares last month when she called the election, saying she wanted strong backing from voters before she launches into tough negotiations with the European Union about Britain’s departure from the bloc.

Monday’s survey for the Guardian newspaper put support for the Conservatives at 49 percent, up two points from the previous ICM/Guardian poll last week, with Labour down one point at 27 percent.

The Conservative lead was the biggest on record for any British election survey conducted by ICM, the polling firm said.

ICM said the centrist Liberal Democrat Party was on 9 percent, up one point from last week, while the anti-European Union UK Independence Party fell two points to 6 percent.

ICM interviewed 2,038 adults online between May 5 and 7.

Pollsters got the result of the 2015 election badly wrong, concluding that they had underestimated support for the Conservatives and had over-represented Labour supporters in their surveys.

ICM’s research director, Martin Boon, said there was now a risk that the latest poll was over-stating support for Conservatives and under-representing the Liberal Democrats.

“With the last two years spent on the development of polling methods specifically devised with the intention of confronting the Labour problem, the question must be considered that we’ve gone too far the other way,” he said.