Prospect represents thousands of members across the civil service and has been vocal in criticising the new civil service pay remit guidelines, published at the end of June, that limit average pay rises to 1-1.5%.

This is significantly below the offers being made to other sections of the public sector and is barely above the 1% pay cap that the government had promised was a thing of the past.

Civil service unions are calling for the guidance to be withdrawn pending fresh negotiations.

Prospect deputy general secretary Garry Graham said: “At a time when many civil servants are facing redundancy due to departmental budget cuts and average pay increases have been capped at a derisory 1-1.5%, public servants will see it as a slap in the face that private sector contractors are coining it in at the expense of staff and the taxpayer.

“Despite the government promising to end the public sector pay cap last year, it is clear that there is still one rule for dedicated public servants who are expected to work for less and less, and another for private sector contractors who can demand as much as they want.

“This shocking revelation is yet another reason why the government must withdraw its misguided and insulting civil service pay guidance and enter serious negotiations about how we can make sure all civil servants get the decent pay they deserve.”