After a year spent trying to persuade two Tory MPs to champion her case against the hospital where her mother died, a retired businesswoman has made a formal complaint to the Conservative party.

Gillian Mackenzie insists Iain Duncan Smith's apparent campaigning verve is simply not mirrored by his parliamentary colleagues. Last night the two MPs denied her claims.

Mrs Mackenzie's 91-year-old mother went into Gosport War Memorial Hospital in 1998 for four weeks' rehabilitation following a hip operation. She died 10 days later. Her daughter claims her death was due to medical negligence, a matter which Portsmouth Healthcare NHS Trust deny.

The Commission for Health Improvement (CHI) is currently investigation the quality of care for the elderly at the Gosport hospital.

Mrs Mackenzie, 64, says that when she tried to enlist the support of the Gosport MP Peter Viggers, she was informed that "Westminster convention" prevented him getting involved and she should contact her own MP in Sussex. Eastbourne MP Nigel Waterson told her to wait for the CHI report.

Mrs Mackenzie said: "They have just been dismissive, totally dismissive. They should at least take a look at the papers. While I appreciate that Nigel Waterson is in a difficult position, Mr Viggers should take an interest in matters involving his own constituency."

Mrs Mackenzie's mother, Gladys Richards, was transferred to the hospital on 11 August, 1998, 12 days after a hip operation. Mrs Mackenzie alleges she was given incorrect medicine and care.

Mrs Mackenzie also turned to the local police. After two investigations the matter was sent to the Crown Prosecution Service, which found there was insufficient evidence.

Mr Waterson said: "There is absolutely no question of this constituent not being offered assistance. I have had some contact with Mrs Mackenzie and tried to be helpful. I am awaiting the outcome of this inquiry. Last time I spoke to her she seemed perfectly content and I am very surprised to hear to the contrary."

Mr Viggers said: "I have never had any complaint about Gosport War Memorial Hospital. The doctors are very dedicated."

Max Millett, the chief executive of the Trust, said last night: "The CHI investigation is welcome. We want to reassure the public that the hospital offers a really good standard of care."