A contest to succeed British Prime Minister Theresa May is heating up as the frontrunner for the post is criticized by rivals for escaping public scrutiny.

Boris Johnson, a former foreign minister under May who resigned last summer, was target of growing criticism on Tuesday when rivals said he should be clearer about his long record of scandals and gaffes.

“I certainly think that everybody who puts their name forward to be prime minister should be open to scrutiny, should be accountable,” said health secretary Matt Hancock whose chances of reaching the final battle for Conservative Party leadership in late July are much lower than Johnson who has a 60-percent probability of winning the top job in the government.

The Daily Mail, Britain’s second-most-read newspaper, said in an editorial that Johnson was deliberately keeping a low profile despite the fact that he has always been trying to be on the headlines.

“Time to come out of your bunker, Boris,” the newspaper said, adding, “Usually he positively craves media attention ... Yet for weeks now he has been stuck in his trench, dribbling out vague policy ideas.”  

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Johnson was the mayor of London until 2016 when he became foreign minister after leading a campaign to win a referendum on leaving the European Union.

He has pledged to implement Brexit on its deadline of October 31, even if it means leaving in a disorderly manner and without a deal with the EU.

His main rival in the Tory Party leadership race is environment secretary Michael Gove who quipped on Monday that Johnson may pull out of the leadership battle just like 2016 when Gove withdrew his support for Johnson.

Johnson has been criticized in the media for a series of scandals in the past, including his extra-marital affairs which he had lied about.

Rivals on Tuesday also has urged Johnson to come forward with more details about his use of banned drugs in the past after Gove admitted to using cocaine some 20 years ago.

Mark Harper, a senior conservative, said the public deserved a "clear answer" from Johnson on the issue when he launches his leadership campaign on Wednesday.