People who have had to wait up to seven years to take part in a bowel screening programme will have to wait several more months to be checked for cancer.

Photo: A. BENOIST / BSIP

A pilot programme run through the Waitemata District Health Board sent invitations to 200,000 people, aged between 50 and 74, to participate.

It successfully screened 117,000 but about 15,000 Waitemata residents did not receive letters about the programme - 30 of whom got bowel cancer. One person has since died.

Among those, 9500 people missed out because of human error, meaning their details were added to a list of inactive and invalid National Health Indicators - people who were either tourists or New Zealanders who had moved overseas.

Ministry of Health National Screening Unit clinical director Jane O'Hallahan said they would be sent apology letters over the coming weeks.

Dr O'Hallahan said invitations to participate in the programme would also be sent, but they would be staggered over the next few months.

"We need to be mindful of the colonoscopy capacity, because there is no point inviting people into a programme where we are unable to move them through the pathway and offer them a colonoscopy in a timely manner."

The Ministry was alerted to the latest error two weeks ago when a member of the public got in touch to ask why they had not been asked to participate.

It's the latest in a series of bungled mail outs - in February, the Ministry revealed 2500 people missed out on screening because invitations couldn't be delivered to their recorded addresses.

More than 600 people were also affected when invitations didn't get sent because of IT issues or problems linked to their National Health Indicator numbers.

That brings the total number of people affected to about 12,500 but the Ministry has put the figure at 15,000 to cover anyone else who may have missed out.

But Bowel Cancer New Zealand spokeswoman Mary Bradley has questioned that figure.

When the Ministry revealed in February that 2500 people missed out because of address issues, there were another 10,000 people whose invitations couldn't be delivered as their addresses were incorrect, she said.

"It seems that 10,000 who were identified in February this year have been put into recall because they haven't been able to track down their addresses.

"So that's 10,000 people who haven't been followed up, that have also been missed off."

Dr O'Hallahan said the Ministry had attempted to find those people but they had likely left the country and were unable to be reached.

Health Minister David Clark is carrying out a review into the pilot programme, and Ms Bradley said the latest error highlighted how important that its findings would be.

"There are so many incidents where errors have occurred and I think it's very confusing - I would wonder whether the Ministry's actually confused about how it's all happening."

Ms Bradley said it was vital the review did not delay the roll-out of further bowel screening across the country.

"The pilot, from 2011 to 2016, did identify 350 people with bowel cancer. That's a lot of lives saved due to being screened."

New Zealand had some of the worst bowel cancer rates in the world and the programme needed to be rolled out nationwide to deal with that, she said.

The Minister's review is due to be completed by the end of June.