Front-line delivery staff will not be hit in the latest round of job cuts

The union, Amicus, says it has seen a document prepared last month containing plans for big redundancies.

Royal Mail has refused to respond officially, saying it will not comment on leaked documents.

The postal service revealed a tenth of its pre-announced 30,000 job cuts would come at managerial level in the form of voluntary redundancies last December.

The mammoth job cull is being executed in an effort to aid the former monopoly to compete more closely with its rivals.

The service - which was paralysed by unofficial strike action last year - currently employs some 200,000 people.

Emergency meeting

Amicus said it believed up to 700 people could be affected.

The union is calling an emergency meeting of its executive to discuss the matter on Tuesday.

A spokeswoman told the Reuters news agency: "We have seen a top-secret document in which Royal Mail plans to renege on the current job security agreement made with us.

"It may lead to compulsory redundancies for managerial staff.

"We have called an emergency meeting of our members and there is a possibility that they will be balloted for industrial action," she said.

It says there is every prospect managers would be balloted on industrial action.