Iain Cockburn spent months caring for his wife before she lost her fight with cancer at the age of 48. But now he is facing a new battle against her employers over the NHS pension the medic paid into for 24 years.

Mr Cockburn, a former Royal Marine, has launched a landmark court case which could cost the Department of Health almost £1 billion in extra pension payments with wider implications for the Treasury regarding public sector pensions.

His wife, Dr Clare Boothroyd died in February 2007. But Mr Cockburn, 56, from Leamington Spa, Warwickshire, receives £3,200 per year less than a woman would in the same circumstances.

His case is being sponsored by the British Medical Association whose legal team argue the case amounts to unlawful discrimination for which there is no reasonable justification.

In an exclusive interview with the Birmingham Post, Mr Cockburn said: “This is purely and utterly sexual discrimination. If on the same day Clare died, a male doctor had died with the same amount of service that she had, having qualified in 1982 without any career breaks, his widow would be collecting £3,000 a year plus pension more than me.

“And this is an NHS pension scheme, so it’s all female employees, not just doctors. It affects nurses, physiotherapists.

“It is any male survivor of a female NHS employee who has been paying into the pension scheme for a reasonable length of time and this could have massive implications.”

The Department of Health admits Mr Cockburn’s pension is less than if he was a widow due to the difference in the way it is calculated.

When widowers’ pensions are calculated, contributions made by deceased female partners before April 6, 1988, are discounted, reducing their entitlement. Widows’ pensions are based on the full contributions made by their male partners.

The Department of Health argues that the difference between the widows’ and widowers’ schemes is “objectively and reasonably justified”.

The more generous provision for widows was justified because of the disadvantaged economic position women held due to child care responsibilities and their historically lower earning potential.

It is now pointing to the potential cost of putting the scheme right retrospectively in its defence in the case.

Mr Cockburn said it was wrong that contributions made by his wife, who worked at Waterside Medical Centre in Leamington Spa, were being treated differently to her male colleague’s payments.

“The contributions Clare made to her pension were the same as her male colleagues,” he said.

“If the pension I should be getting is money that Clare had already earned and I am not getting it, who is? Where is that odd £3,000 a year going? She earned it, not another doctor.”

Mr Cockburn, who married Clare in 1992 after a two year relationship, gave up his job in IT and became her full-time carer when she was diagnosed with a malignant melanoma, four years after overcoming breast cancer.

“It was aggressive and it was a secondary cancer,” he said. “She had previously had breast cancer but this was a malignant melanoma but not one that you or I would recognise. This was a tumour way up inside her right nostril, internally. Melanomas are skin cancers but this was inside the nose, almost as level with her eye.

“In the space of a weekend she went from being fine to having a fairly large swelling on the side of her nose and a fairly constant nose bleed. That was start of the second cancer.

“The situation developed over the weekend. On the Monday, she made a phone call, she saw a consultant on the Tuesday morning and they had done the first operation by the end of the week.

“Clare had surgery on her face and chemotherapy, she was treated at the old Queen Elizabeth Hospital in Birmingham, but the cancer spread below the neck. We were told, ‘it’s terminal – if you have anything planned, do it now’.

“At the time I flipped into what is called ‘carer mode.’ I had to do what I had to do. I gave up work to look after her and we did all the things she wanted to do.

"We put together a ‘bucket list.’ Clare learnt to ride a motorbike and we bought her one which she got to ride three times and I still have her bike.

“We nearly travelled the world. We had a trip planned and got to India but we were there for a week before we had to come home.

"In the space of that week Clare went from being a normal size 12 to 14 slim female to looking like she was six months pregnant, the tumour grew so big. She said ‘get me home’ so we did.”