Image copyright Getty Images Image caption Breast cancer screening is offered once every three years to women aged 50 to 70

More than 8,000 calls have been made to a helpline since it was revealed that 450,000 women were not invited to routine breast cancer screening due to a computer error.

Public Health England says it was not aware of a national problem with the screening programme until January.

But the BBC understands that two NHS trusts in England raised concerns about IT issues as early as March 2017.

They were told the problems were a local - not national - matter.

It is understood the IT problem related to an algorithm used to decide the order in which to send letters to women of different ages.

The national screening error, which dates back to 2009, meant women aged 68 to 71 were not sent letters inviting them to their final screening appointment.

Breast cancer screening is currently offered once every three years to women aged 50 to 70 in the UK.

Health Secretary Jeremy Hunt said that up to 270 lives may have been cut short because of the mistake.

The 309,000 women affected - those who are still alive - would be contacted by letter by the end of May with the offer of catch-up mammograms, he said.

Breast cancer survivors are demanding answers and experts are asking why the error was not spotted sooner, as cancer charities are being inundated with calls.

Media playback is unsupported on your device Media caption Helen Jarvis experienced problems with the helpline

'Extremely worried'

Breast Cancer Care said its helpline had received four times its usual number of calls in one day.

Clinical director Dr Emma Pennery said women contacting them were feeling "angry and confused".

"Many are anxiously playing a waiting game until the letters arrive, not knowing if they've been affected.

"Others are extremely worried about when their letters will arrive and how long it will take to get screened."

Cancer experts have cautioned that there are pros and cons to screening - not all cancers are picked up by screening and sometimes those picked up do not need to be treated.

If you think you may be affected:

call the breast screening helpline number 0800 169 2692

go the NHS Choices website for more information

you should receive a letter by the end of May

'She wondered why she hadn't been called'

Helen Baczkowska's mother Ann died of breast cancer in 2014, aged 74, after being diagnosed in 2012. She was registered with a GP but had not had a mammogram for several years. Helen fears she may have been one of those overlooked by the screening programme:

"I remember having conversations with her where she said, 'you know what, I haven't been called for a screening for some time', and there was just a question in her mind as to why she hadn't been called, and then of course she discovered a lump herself.

"We think she may have tried to inquire, but didn't really know who to speak to as it didn't come through the GP, it's a separate system.

"You never know with someone's cancer whether it could have been very aggressive anyway. There are so many variables.

"It's hard to lose somebody and to have tried to have moved on through your grief and then have it all brought back."

Lee Towsey's mother died of breast cancer in 2012, aged 70, having found a lump. She did not have a mammogram around the time that she should have done.

Mr Towsey feels that the whole screening process was badly organised.

He said: "I don't know where to take it from here, but I need to talk to my family.

"I mean, it's outrageous, it's disgusting, and I think that someone needs to resign, to be honest.

"It's like it doesn't matter that 270 women died, it just doesn't matter. Who cares?"

Sara Hiom, director of early diagnosis at Cancer Research UK, said the women affected would have missed "the final of what could have been seven rounds of screening".

"If we assume that they attended every other screening round that they would have been invited to from the age of around 50, then they have at least had several opportunities to have any breast cancer diagnosed earlier."

'Devastated'

A recent report on the NHS found that the number of women who accepted invitations to breast screenings had fallen to 71%, a 10-year low.

The Institute for Public Policy Research (IPPR) has questioned why health chiefs did not raise any alarms.

Public Health England spotted the issue in January while analysing data from the Age X trial - which was testing the idea of screening women up to the age of 73.

The BBC understands an error led to women in the control group wrongly being offered screenings up until their 70th birthday, rather than their 71st.

Dr Jenny Harries, deputy medical director of Public Health England, told BBC Radio 4's Today programme: "There are a number of organisations involved in this and I think we are all - Public Health England, the NHS, NHS Digital, the Department of Health - devastated by this.

"We have a screening programme that is world-class.

"We wouldn't want any lives to be shortened. We have gone back and fixed all these glitches and audited that, so women can be assured going forward that that is sorted."