A helpline set up with the backing of Princess Diana and The Independent, offering support to women with hereditary breast cancer is under threat after NHS trusts have withdrawn funding.

Cancer specialists, genetics experts and a former Secretary of State for Health have championed the National Hereditary Breast Cancer Helpline which they say is irreplaceable. It costs £63,000 a year to run and provides a nationwide, round the clock service but one in three Primary Care Trusts have declined to pay the £422 annual cost.

The helpline’s founder and organiser, Wendy Watson, was the first woman to undergo preventive mastectomy in the UK because of her high genetic risk. She became a national figure after her case was featured in The Independent in 1994.

Ms Watson had both her breasts and ovaries removed at the age of 38 and her daughters also chose mastectomy when they reached adulthood. The three women now run the service from Mrs Watson’s home near Bakewell in Derbyshire, with the help of 500 others who have had similar experiences and 4,000 supporters. They say they have taken 80,000 calls over 14 years.

About 5 per cent of women have a raised genetic risk for breast cancer that gives them up to an 85 per cent chance of developing the disease over their lifetime. The discovery leaves women facing agonising decisions, such as whether to remove their breasts and ovaries to avoid the risk.

Andy Burnham, a candidate for the Labour leadership, used the helpline when he was health secretary and his wife, Marie France van Heel, was found to be carrying a gene dramatically increasing her risk of breast cancer. She had both breasts removed in June.

Mr Burnham wrote to Wendy Watson: “I am in great admiration of your work and determination over the years to bring this important matter to prominence. Your work to support women and their families is tremendous and long may you continue.”

The helpline has also won backing from Professor Gareth Evans, chair of the guideline committee of the National Institute for Clinical Excellence (Nice) , which in 2006 issued advice on the care of women at high genetic risk of breast cancer saying that they should be put in touch with other women who had been in a similar position.

He said: “Wendy pioneered the way of thinking when the overwhelming weight of medical opinion was against her. She set up the helpline because there was no help or advice for her when she was going through it all those years ago. That is what the National Hereditary Breast Cancer Helpline is all about and that is why we need to fight to keep it.”

Lester Barr, consultant breast surgeon at Christie Hospital, Manchester and chair of the Genesis Breast Cancer Prevention Appeal, said : “The best support for patients [at genetic risk of breast cancer] comes from Wendy’s helpline. She has great insight, having been through it herself, and she believes passionately in what she does. She does it very well.”

Ms Watson said today: “I do a lot for the helpline free of charge but the last few years have been a nightmare in terms of raising funds. I have to get up each morning and think, how many PCTs can I face arguing with today?”