Capita took over the Public Service Pensions Scheme from company MyCSP in December and said it had inherited a backlog of 86,000 cases – 49,000 more than expected – and more than 20,000 pension quotations are still outstanding, according to the Cabinet Office.

An emergency interest-free loan system of up to £10,000 was set up in January to try and tide pensioners over until issues were resolved, which has so far paid more than £7.2m, the Cabinet Office said.

The Cabinet Office said the service levels since the contract transfer in December were “unacceptable”.

“An urgent recovery plan is under way, and our immediate priority is to stabilise the service and give current and former civil servants the service they deserve,” a spokesperson said.

Capita has committed to restoring a normal level of service by the end of June.

A spokesperson said it had been working with the Cabinet Office over several months to reduce the backlog.

“Additional staff have been trained and deployed, and our focus is on ensuring members of the Civil Service Pension Scheme receive the service they expect and deserve, in line with the plan agreed with the Cabinet Office,” they said.

“We are sorry for the worry, distress and frustration any delays are causing.”