Media playback is unsupported on your device Media caption The Prime Minister says being home secretary is "one of the toughest jobs in government"

The government is to investigate whether Home Secretary Priti Patel has breached the ministerial code, amid allegations of bullying.

Cabinet office minister Michael Gove confirmed the inquiry after an urgent question from Jeremy Corbyn.

It comes after bullying claims were made by the ex-top civil servant in Ms Patel's department.

Mr Corbyn said he believed Ms Patel - who has previously denied she mistreated staff - should be sacked.

Sir Philip Rutnam, the Home Office's most senior official, resigned on Saturday citing a "vicious and orchestrated" campaign against him.

The BBC has also learnt that a formal complaint about Ms Patel's conduct was made when she was employment minister.

She has not made any public comment since Sir Philip announced his resignation.

In the Commons, Mr Gove said Ms Patel "absolutely rejects these allegations".

"The prime minister has expressed his full confidence in her and having worked closely with the home secretary over a number of years, I have the highest regard for her - she is a superb minister doing a great job," he said.

"This government always takes any complaints relating to the ministerial code seriously, and in line with the process set out in the ministerial code the prime minister has asked the Cabinet Office to establish the facts."

He added: "We make no apology of having strong ministers in place."

'Part-time PM'

But Mr Corbyn said that if Sir Philip Rutman allegations about the home secretary's conduct are true "they would constitute a clear breach of the code".

"So why, without a proper investigation has the prime minister defended the home secretary calling her 'fantastic' and saying he 'absolutely' has confidence in her?

"It's not enough just to refer this to the Cabinet Office. The government must now call in an external lawyer.

"A minister in breach of the ministerial code cannot remain in office and should be dismissed."

Media playback is unsupported on your device Media caption Jeremy Corbyn: Government 'led by bullies'

He said the "truth" was that this government "is led by bullies presided over by a part-time prime minister" who "cannot be bothered to turn up".

"The integrity and credibility of the government is on the line," he said.

In his statement on Saturday, Sir Philip said he received allegations that Ms Patel's conduct towards employees included "swearing, belittling people, making unreasonable and repeated demands".

He said he now intended to take legal action against the Home Office on the basis of constructive dismissal, alleging that he had been forced out of his job.

The First Division Association union, which represents senior civil servants, earlier called on Cabinet Secretary Sir Mark Sedwill to launch an "independent" inquiry into Ms Patel's behaviour.

The union's general secretary David Penman said a probe should be led by an external lawyer, with access to ministers' and special advisers' communication records.

In a letter to Sir Mark, he also said there was a need for "urgent reform" of the process by which civil servants can raise complaints about ministers.

Speaking during a visit to Public Health England in North London on Sunday, Mr Johnson said he "absolutely" has confidence in Ms Patel.

"I think she's a fantastic home secretary" he said.

Media playback is unsupported on your device Media caption Sir Philip Rutnam says there has been a "vicious, orchestrated briefing campaign" against him

The BBC's home affairs correspondent Danny Shaw has also learnt that a formal complaint about Ms Patel's conduct was made when she was employment minister at the Department for Work and Pensions. The substance of it is not known, nor whether it was substantiated or followed up.

The complaint is believed to have been made by a member of her private office - a team of six to eight civil servants which works closely with an individual minister.

A spokesman for Ms Patel said she was "not aware" of the complaint and the government, while it did not deny the claim, said it would not comment on personnel issues.

Image copyright PA Media Image caption Ms Patel has not yet commented on Sir Philip's statement

One Whitehall insider said Ms Patel had created a "hostile and unhappy" environment for civil servants there by questioning their capability and undermining their performance.

"I felt very sorry for people in her private office - they felt bullied," they said.

BBC political correspondent Iain Watson said allies of Ms Patel are privately suggesting that Sir Philip was not up to the demands of the job.