Britain’s civil service union has urged Andy Burnham to strip himself of the power to rule on bullying complaints against ministers.

The FDA is warning that Whitehall officials are often too frightened to come forward because they do not trust the system.

FDA general secretary Dave Penman, in a letter seen by The i Paper, tells the incoming Prime Minister existing arrangements leave ministers effectively policing themselves and are no longer fit for a modern workplace.

It comes as Burnham’s team is expected – before he appoints a Cabinet – to be handed a copy of a secret Labour “Pestminster” dossier containing allegations of bullying, harassment and inappropriate behaviour against more than 30 Westminster figures.

The letter, sent ahead of Burnham’s appointment as Prime Minister on Monday, calls on him to break with his predecessors by establishing a fully independent process to investigate bullying and harassment allegations against ministers.