Brendan O'Hara told Westminster that Jamie Dalgleish, 65, retired last year after 25 years in the submarine service and 23 in the MoD Police but still has not received his civil service pension.
Dalgleish has taken a minimum-wage job cleaning dog kennels for the MoD Police, which O'Hara cited as evidence of the financial hardship caused by stalled pension payments.
A government minister called the case "totally unacceptable" and said he would take it directly to Capita, which has administered the Civil Service Pension Scheme since December.
Capita said last week it could lose up to £40 million fixing the failures, apologised for poor service and said new processes, automation and technology are now in place to clear the backlog.