A review into a major blunder in the breast cancer screening programme which meant thousands of women were not invited to final screenings has found that the announcement was made following advice based on an incomplete understanding of what had happened.

The error was said to have affected an estimated 450,000 women and to have potentially led to hundreds of lives being cut short when it emerged in May.

Then-health secretary Jeremy Hunt told the Commons a “computer algorithm failure” dating back to 2009 meant many women aged 68 to 71 were not invited to their final routine screening.

Jeremy HuntJeremy Hunt (Victoria Jones/PA)

But an independent review, published on Thursday, has found there was no computer algorithm failure, and that the IT systems used – although described as “dated and unwieldy” – had broadly operated as they were designed to.

Instead, it found the misunderstanding arose because of a specification document written in 2013.

This said women should be invited for screening “within 36 months of their previous screening, until they reach the age of 71”.

In the opinion of the review, this document was based on a misunderstanding of how the programme was being delivered in practice, with local screening units continuing to understand the upper age limit as 70, and to communicate this to women in invitation letters.

The report said up to 67,000 women may have not been invited to a final screening, but NHS England has assured the panel that all these women have since been invited to a catch-up screening.

It said no one person, or body, was to blame for the confusion, but in the rush to announce and correct the issue, assumptions were made about policy and operations which were not sufficiently challenged.

The report makes recommendations including clarifying the age when women should stop being invited to screenings, updating public information so it is clear to women what they should expect from the screening programme, and reviewing the governance of all national cancer screening programmes.

It also suggests making IT systems simpler for breast screening units to use, and putting in place a structure to ensure that IT systems work together to deliver the programme as well as other screening programmes.

These recommendations will inform the recently announced broader review of national cancer screening programmes led by Sir Mike Richards.

The review team visited 10 breast screening units, where they said they found staff were skilled, experienced and worked hard to make sure women in their care received the best possible service.

The review was co-chaired by Lynda Thomas, chief executive of Macmillan Cancer Support, who said: “We know that the announcement in May of a breast screening incident caused anxiety for thousands of women, sometimes unnecessarily, and it was of critical importance that their voices and concerns were heard as part of this independent review.

“It is completely unacceptable that there was confusion about what the breast screening programme should have been delivering.

“There needs to be clarity, and importantly women need clear information about what they should be able to expect.”

The review was commissioned by Mr Hunt in May.

Co-chairman Professor Martin Gore, of Royal Marsden NHS Foundation Trust, said: “The NHS breast screening programme is one of the best in the world, and the staff who deliver it work exceptionally hard to give women the best care.

“However, the supporting systems and governance processes need to be updated.

“It is essential that Public Health England as a matter of urgency works with the women they contacted and have been diagnosed with breast cancer, their families and their healthcare professionals, to find out whether they were harmed by any errors in the breast screening programme, and are given the support they need.”

Baroness Delyth Morgan, chief executive at Breast Cancer Now, said: “After months of uncertainty, it is totally unacceptable – and extremely concerning – to learn that hundreds of thousands of women have been unnecessarily caused such significant distress.

“This has been nothing short of a system failure, precipitated by a lack of clear ownership and strong leadership of a world-leading programme. It highlights a continued inability, amid structural confusion, to monitor what is happening in the screening service.

“The NHS Breast Screening Programme remains critical to early diagnosis in this country, preventing 1,300 deaths from breast cancer each year – and it must not be left on the shelf.

“We simply cannot let bureaucracy or a lack of leadership stall our progress on breast cancer, whether in adopting research advances or in ensuring a world-class early detection programme.”

Samia al Qadhi, chief executive of Breast Cancer Care, said: “While it’s a relief the number of women affected by the breast screening incident is dramatically fewer than expected, it is exasperating that hundreds of thousands across England have been caused needless distress and anxiety for months.

“It is incredibly disconcerting that there is a total lack of leadership and accountability for such a crucial programme for women’s health. Having fragmented responsibilities without a sense of a bigger picture is worrying as this can open the door to such appalling mistakes.”