The invitation follows months of pressure from the Prospect union, representing public service professionals, for improvements to the civil service pay structure, Treasury remit process, and in particular, pay and grading systems for specialist groups like scientists, engineers, vets and heritage workers.

Dai Hudd, Deputy General Secretary, said: “The current pay system is dysfunctional and inconsistent. Unwarranted differences in pay between different agencies and departments, clumsy structures and the 2% limit on basic pay have created huge strain for our members.

“We are not looking for miracles but we are looking for progress towards a fairer long-term system.

“Specialists need a pay structure that matches their distinctive employment needs on issues like training and career development with the employers’ long-term need for a skilled workforce.”

The letter from the Cabinet Office to Prospect accepts that there are “concerns” about the more than 200 delegated bargaining units in the civil service, which it concedes “may lead to some inefficiency.”

The talks with Prospect will take place in the context of discussions between the Council of Civil Service Unions, the Cabinet Office and the Treasury over the coming weeks. It is hoped any progress will be reflected in the 2009 pay remit guidance for the civil service, due out in early February.