A British clinic says it has seen a rise in preventative mastectomies in at-risk women since actress Angelina Jolie had the operation and wrote about it.

Hollywood actress Angelina Jolie's decision to undergo a double mastectomy has prompted other women to have the procedure, a British clinic says.

Researchers at Genesis Prevention Centre Family History clinic in Manchester say they have seen a rise in the number of women having preventative double mastectomies over the past few years.

Jolie announced in May 2013 that she had undergone a double mastectomy to reduce her chances of getting breast cancer.

The mother-of-six wrote in the New York Times that doctors had estimated she had an 87 per cent risk of breast cancer and a 50 per cent risk of ovarian cancer because of a faulty hereditary gene.

"I decided to be proactive and to minimise the risk as much I could," she wrote.

In a letter to the editor, published in the open access journal Breast Cancer Research, researchers from the Genesis Prevention Centre said preventative double mastectomies at the clinic more than doubled from January 2014 to June 2015.

There were 83 procedures performed during this period, up from 29 between January 2011 and June 2012.

Women who carry the BRCA1 or BRCA2 genetic faults have a higher risk of breast and ovarian cancer.

The experts said they have also seen the "Angelina effect" in a higher number of referrals to the clinic, which covers a population of five million.

They said: "Although the main impact of the Angelina effect was from June to November 2013, this trend continued through 2014 with increased referrals from 201 in January-June 2012 to 388 in January to June 2014, and rising by 366 for the last six months, to give a total of 754 for 2014.

"Women attending for risk assessment and discussions concerning bilateral risk-reducing mastectomy, unprompted, still mention the effects of Angelina Jolie on their attendance anecdotally to clinic physicians and still reflect on the impact of her speaking publicly in their pre-surgery consultations with the clinical psychologist in 2015."

Lester Barr, chairman of Genesis Breast Cancer Prevention, said: "These observations are particularly interesting as they demonstrate that women who were referred for gene testing in the months after Angelina's story broke went on to have a preventative mastectomy.

"It means that Angelina's announcement did not simply lead to a knee-jerk reaction in those at risk from breast cancer, but encouraged them to find out more about the procedure and what steps they would need to take to reduce their risk."