The move would be controversial, since it would strengthen incentives for doctors to work at private firms, and remove a key feature differentiating NHS and private services.

Assura Medical, recently bought by Sir Richard Bransons Virgin empire, is among firms pushing for a change in the rules forbidding private firms from offering NHS pensions to directly employed medical staff.

Pressure on politicians to change the rules came as Pulse learned some sessional GPs working for Assura had been earning NHS pensions in breach of existing regulations.

In Bath, GPs working for an out-of-hours operation run by Assura have been told their pension agreements, in place since the opening of a GP-led health centre in April last year, will have to be ripped up.

In a letter obtained by Pulse, Amanda Simpson, business director of Assura Minerva, the limited liability partnership running the centre, told GPs it had acted in good faith and had believed the pensions arrangement was bone fide because of precedent set at other Assura GP-led health centres.

She added: Unfortunately, NHS Pensions has now advised us payments for all work done on a sessional basis cannot be included in the NHS Pension Scheme.

The letter goes on to promise staff the company will find an alternative way of providing an NHS pension as we still believe it to be a valid entitlement.

But NHS Pensions told Pulse the payments flouted rules set up to keep NHS pensions with the 10,000 recognised NHS providers, including 8,000 GP practices, and forbidding private firms gaining access to NHS pensions for sessional GPs.

Ross Mathieson, the bodys compliance manager, said: The rules are quite clear. If youre a fee-based GP working for a private company, youre not entitled to an NHS pension.

Pulse has learned that a Department of Health consultation on access to NHS pensions is coming under pressure to change the rules.

Bart Johnson, chief executive of Assura Medical, said: We welcome the fact the DH and Treasury are looking into this. It seems entirely reasonable that staff who have been providing services to the NHS should get NHS pensions. Whoever wins the election, we want to be part of the discussion.

Dr Andrew Dearden, chair of the BMA pensions committee, said private firms were increasingly looking to attract staff by finding alternative ways to offer NHS pensions.

'Its no surprise that they are trying to find alternative ways. They see it as a recruitment incentive', he said.

Richard Hoey, editor of Pulse, said: Whoever is the incoming government will come under strong pressure to allow private companies access to NHS pensions and its decision will send a strong signal about how it views the role of the private sector in our health service.

It would be highly unusual to allow private sector employees access to public sector benefits, and would break down one of the symbolic barriers between public and private sector in the NHS.