The FDA senior civil servants’ union has been given permission to launch a challenge against Johnson’s decision not to sack Patel after an investigation found she broke the ministerial code.

Lawyers for the union, which brought the case against the PM, said in court that the government had attempted a “ragbag of arguments” to claim that Johnson’s decision did not need to be reviewed.

The FDA’s general secretary, Dave Penman, said he was “very pleased” at the court’s decision to grant a judicial review on the ministerial code, saying Johnson had “erred” in his interpretation of it.

“The ministerial code is the only means by which civil servants can raise complaints against the conduct of ministers, and it is vital that decisions on this are subject to the rule of law,” he said in a statement

A bullying row blew up around Patel in February last year, after Philip Rutnam, the top civil servant in the Home Office – her department – dramatically resigned, claiming there had been a “vicious and orchestrated briefing campaign” against him.

Johnson, the arbiter of the ministerial code, asked his independent adviser on ministerial standards, Alex Allan, to investigate claims of bullying by Patel.

The results of that inquiry, published in November 2020, found Patel had occasionally engaged in behaviour “that can be described as bullying” and, as a result, had breached the code, “even if unintentionally”.

Allan later resigned, after Johnson sided with the Home Secretary on the matter by not sacking her and said he did not believe she was a bully.