Mr Ryall said work was under way to identify workforce development needed for a nationwide programme, a chief constraint to which was colonoscopy capacity.
Dr Derrett said the four-year pilot was too long, and any pilot ought to have been nationwide. This would have been the catalyst for health boards to build up their endoscopy workforce.
She saw no evidence the workforce was being built to prepare for a nationwide rollout.
Nurse practitioners could be trained to perform colonoscopies, as they were in some places overseas.
"Where are the training programmes ... how are they ensuring that we have the workforce to respond to this tragedy?"
Waiting until near the end of the four-year pilot to decide whether to roll it out was unacceptable, she said.
Pharmacy bowel cancer testing kits played a role, but could not replace a screening programme.
"Each year, 1200 New Zealanders die from bowel cancer; as many as 400 of these deaths could be prevented if the Waitemata screening was available nationally."