But yesterday, pensioners, most of them in London, Glasgow and the North- west, received Girocheques dated to be cashed in 1995. Post Offices were unable to honour them.
A Benefits Agency spokeswoman said: "It was a computer problem and we are extremely sorry about this, and regret any distress caused. We hope to have it sorted out within the next few days."
The agency is an executive body of the Department of Social Security but is answerable to Secretary of State for Social Security, Harriet Harman.
Last night the Tories sought to blame Ms Harman for the "fiasco". The party's social security spokesman, Simon Burns, said Post Offices had reported many pensioners were distressed.
"Harriet Harman has repeatedly tried to make political capital out of the Government's cold-weather payments. This is symptomatic of the overall confusion in the Government's welfare policies," he said.
Mr Burns said he would be tabling parliamentary questions to find out how many pensioners were affected and how much the error would cost to correct.
A DSS spokesman said the agency was responsible for the procedural implementation of benefits policy. Ms Harman had been made aware of the problem.