LONDON (Reuters) - British ministers rallied around Boris Johnson on Sunday, saying the foreign secretary was doing a “great job” and had no reason to resign over remarks that critics say may prompt Iran to extend the prison sentence of a jailed aid worker.

Britain's Foreign Secretary Boris Johnson waits to lay a wreathe at the Remembrance Sunday Cenotaph service in London, Britain, November 12, 2017. REUTERS/Toby Melville

The coordinated defense is part of attempts to shore up the government of Prime Minister Theresa May, weakened by a series of scandals and gaffes involving her top team of ministers as she negotiates Britain’s departure from the European Union.

The leader of Britain’s main opposition Labour Party, Jeremy Corbyn, called on May to sack Johnson, writing in the Observer newspaper on Sunday that “we’ve put up with him embarrassing and undermining our country through his incompetence ... for long enough. It’s time for Boris Johnson to go”.

Corbyn, and London Mayor Sadiq Khan, also a Labour member, said Johnson had offended states and religions before “bungling” the case of Iranian-British aid worker Nazanin Zaghari-Ratcliffe, in prison after being convicted of plotting to overthrow Iran’s clerical establishment. She denies the charges.

But two of his allies, Brexit minister David Davis and environment minister Michael Gove, defended Johnson, who last week said he could have been clearer in his remark that Zaghari-Ratcliffe had been teaching people journalism before her arrest in April 2016.

Zaghari-Ratcliffe’s employer, the Thomson Reuters Foundation, a charity organization, said Johnson’s comment made on Nov. 1 was incorrect, while opposition British lawmakers said the remarks could land the aid worker a longer term in jail.

The Thomson Reuters Foundation is independent of Thomson Reuters and operates independently of Reuters News.

“Why would you want to sack him? He’s a good foreign secretary,” Davis told Sky News.

Gove urged critics to stop focusing on Johnson’s role in the case and instead to question the motivation of what he called “the Iranian regime” in jailing Zaghari-Ratcliffe.

“There is no reason, no excuse and no justification for her detention and she should be released,” he told the BBC’s Andrew Marr show.

A Foreign Office source later said Johnson had held a “very constructive” phone call with her husband, Richard Ratcliffe, who has called on the minister to visit his wife in jail.

The show of support for Johnson from fellow Brexit campaigners demonstrates the difficulties May faces in keeping her cabinet unified on a range of issues.

She lost two of her ministers in a week: Michael Fallon quit as defense minister in a growing sexual harassment scandal and then Priti Patel was forced out of her job as aid minister over undisclosed meetings with Israeli officials.

Forty members of the Conservative Party have agreed to sign a letter of no-confidence in the prime ministers, eight short of the number needed to trigger a leadership contest, the Sunday Times newspaper reported.