Boris Johnson has ordered an inquiry into allegations that Home Secretary Priti Patel has breached the ministerial code following claims of bullying.
Ms Patel has faced questions over her conduct following the resignation of Sir Philip Rutnam on Saturday, in which the formerly senior civil servant made a raft of allegations against her.
The Home Secretary has previously denied having mistreated staff.
Minister for the Cabinet Office Michael Gove announced on Monday afternoon an investigation to "establish the facts" had been launched.
Addressing questions from the opposition in the Commons, Mr Gove 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."
The Prime Minister has stood behind Ms Patel, and Mr Gove reaffirmed his confidence in his Cabinet colleague as well.
“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," said Mr Gove.
Over the weekend, Sir Philip, who was the most senior official in the Home Office, said he planned to take legal action over claims of constructive dismissal.
Labour leader Jeremy Corbyn said if the “serious allegations” raised by Sir Philip about the Home Secretary’s conduct are true “then that would clearly constitute a breach of the ministerial code”.
He added: “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, as quite rightly suggested by the union for senior civil servants, the First Division Association.
“A minister in breach of the ministerial code cannot remain in office and should be dismissed."
Amid the furore, Dave Penman, general secretary of the FDA union – which represents senior civil servants, said the issue must not be allowed to become a political football.
He said: “I’m not sure that debate in Parliament will have done anything to reassure civil servants that any concerns they have on ministerial bullying are anything other than a convenient political football to kick between the Govt and opposition benches.”
