Britain's Prime Minister Theresa May tours the UTC Aerospace Systems factory with General Manager Robert Hupfer and West Midlands Mayor Andy during a campaign in Wolverhampton, May 6, 2017. REUTERS/Jack Taylor/Pool

LONDON (Reuters) - British Prime Minister Theresa May maintained her strong lead in opinion polls ahead of next month’s national election, with one analyst saying she was on course for the kind of huge success Margaret Thatcher enjoyed over 30 years ago.

May is asking voters to strengthen her hand as she seeks a mandate for her plan to implement the result of last year’s Brexit referendum by quitting the European Union’s single market.

Her Conservative Party made big gains in local elections last Thursday at the expense of the main opposition Labour party and polls published at the weekend, conducted beforehand, showed her with a commanding lead of up to 19 percentage points.

May has a working majority of less than 20 seats in the 650-seat parliament but polling analysts have predicted she could increase that number by as many as 100 at the June 8 election.

“... as the local elections showed, they are ... are on course for the type of victory last seen by (Labour’s) Tony Blair and Margaret Thatcher when they were at their peaks,” said Adrian Drummond of pollsters Opinium.

Opinium had the Conservatives 16 percentage points ahead of Labour on 46 to 30 percent of those surveyed but another poll by YouGov for the Sunday Times newspaper put them 19 points clear, a six-point increase over last week.

An ORB poll had the Conservatives extending their lead over Labour by four points to 15 percent.

Thatcher, Britain’s first woman prime minister, was one of the Conservatives’ most dominant leaders of the post-war years between 1979 and 1990.

Blair, Britain’s longest-serving Labour prime minister, was in office between 1997 and 2007.