Director of the National Health Service bowel cancer screening programme's hub, Prof Stephen Halloran, said there was already scepticism that the recently announced extension of the programme could damage the current screening programme.
It was announced this month FS would be offered in addition to the faecal occult blood testing already offered in the programme.
This follows major UK research published last year showing promising reductions in both the incidence of colorectal cancer and deaths from it using FS.
At this stage in the UK while there were strict quality controls about how colonoscopies should be performed, such measures had not been put in place for FS, Prof Halloran said.
In a screening programme, people needed to know that wherever they received a procedure it was done to a consistent standard.
Prof Halloran said it had to be remembered that with a screening programme it was not actually the type of initial test which was most important, but getting the whole of the system to work well.
In New Zealand to add to advice he has been providing from afar to the Ministry of Health on its four-year plans for a bowel cancer screening pilot in the Waitemata, due to start in October; Prof Halloran said he thought the plans were "looking good".
He was confident the ministry's decision to stick with the immunochemical faecal occult blood test for the pilot was the correct one.
The Cancer Society of New Zealand health programme manager, Dr Jan Pearson, said the society would like to see both the immunochemical faecal occult blood test and flexible sigmoidoscopy tested in the pilot study.
