The company has refused to comment on how much the managers, who have offices in An Post's resource centre at Townsend Street, Dublin 2, are paid. It said the managers were assigned to "various projects from time to time". It is understood, however, that they each earn between 50,000 and 75,000 a year.

Union sources conceded that the managers "don't have a job title" but said they were involved in strategic work.

The Labour Court recently described the situation as "unusual and in some respects unique".

It has also emerged that the managers' union, the Association of Higher Civil and Public Servants (AHCPS), has taken the company to the Labour Court in an attempt to block its attempts to abolish their shift pay allowances.

The managers, who were previously employed in the company's mail processing operations, receive the payments even though they no longer work shifts. Their union is arguing that the managers are entitled to the payments under the terms of the company's restructuring agreement, which stated that workers would not suffer any loss in pay.

The company is unable to make the managers redundant under the terms of the agreement as it allows for voluntary redundancies only. The 10 managers have refused to take voluntary redundancy or early retirement.

A spokesman for the AHCPS said the union was unable to comment on the matter due to ongoing negotiations with An Post.

A spokesman for An Post said the company "has not yet introduced a policy of compulsory retirement as there has not been a requirement to date".

The spokesman insisted that the company had not attempted to remove the managers' allowances.

However, according to a Labour Court recommendation issued last month, "the company's case [in the dispute] is that, as the workers are no longer doing the shift / on-call duties which merited the allowance, there is no reason to pay the allowance".

A spokeswoman for the Minister for Communications, Noel Dempsey, said it was an "operational matter" for An Post and it would not be appropriate for the minister to comment on it.

Fine Gael's communications spokesman, Bernard Durkan, said the case demonstrated that all aspects of the management of An Post needed to be reviewed.

"We must put the work practices and management structures in place so that An Post can compete effectively after deregulation of the postal market, " Durkan said.