Responding to the comments from government sources, Prospect general secretary Mike Clancy said:

“It is alarming that government sources are threatening to tear up purdah rules if an election is called and seeking to abuse the work of civil servants during this highly sensitive times.

“Rules on purdah are designed to protect civil servants, politicians and the public from claims that the legitimate work of government is being abused to support one party over another.

“Clearly, civil servants will continue to work behind the scenes on whatever priorities the government sets, including to mitigate a No Deal situation, but we need urgent clarification that ministers will respect the professionalism and impartiality of public servants.

“We already face the prospect of the nastiest election in living memory. Civil servants have been attacked form all sides in recent months and are unable to answer back, and the main parties have refused to confirm that they will respect the independence of the civil service.

"Cabinet Office needs to now urgently clarify that government will stand by purdah rules in an election is called.”

Prospect and senior civil service union the FDA wrote to all political parties in July asking for them to commit to protect the independence of the civil service. Only Plaid Cymru have replied to the letter.