A union representing senior public servants has been given the go-ahead to bring a High Court challenge against the government.
The FDA union launched judicial review proceedings in February over the prime minister’s decision to disregard the findings of his adviser on ministerial standards last year.
Sir Alex Allan left his advisory role in Downing Street after Johnson contradicted his advice by judging that Patel did not breach the rules, despite being found to have bullied staff.
At a hearing in London on Tuesday, Mr Justice Linden granted the FDA permission for a full hearing of the judicial review claim.
The FDA is challenging Boris Johnson’s decision that Patel’s conduct did not breach the ministerial code.
Mr Justice Linden said that, while it is arguable that Johnson was entitled to rely on his own interpretation of the word “bullying” when reaching his decision, it is also arguable that the court may be persuaded that the word should be interpreted in the context of the Civil Service staff policies.
The judge who hears the full case will also have to decide whether the court is capable of determining the issue and whether the FDA has standing to bring the claim.
Dave Penman, the union’s general secretary, said in a statement: “We are very pleased that Mr Justice Linden has today granted permission for a full hearing in our judicial review.
“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.
“Ministers should be held to the same standards of conduct as civil servants.
“We welcome the opportunity now granted to argue that point fully that the prime minister erred in his interpretation of the ministerial code when deciding that the Home Secretary did not break the code.”
Penman said in February that the affair had obliterated Civil Service trust in the ministerial code.
He said a survey taken of FDA members who are most likely to work with ministers found that nearly 90% said they had no confidence in the ministerial code as a mechanism for dealing with bullying and harassment by ministers.