The union for senior civil servants has urged Rishi Sunak to reform the ministerial complaints system, amid allegations of bullying by ministers.
In a letter, Dave Penman of the FDA said a more transparent and independent system is needed to stop a “drip feed” of claims about ministers’ conduct.
He does not mention Dominic Raab but it comes after bullying allegations were made against the justice secretary.
The PM has said he is unaware of any formal complaints against his minister.
A spokesman for Mr Raab also reiterated that the justice secretary and deputy prime minister had not been made aware of any formal complaints against him. He added that Mr Raab “holds himself to the highest standards of professionalism” and enjoys good working relationships across Whitehall.