National Party leader Judith Collins has called director general of health Ashley Bloomfield a "one-trick pony" after Bloomfield's belated revelations about his discussions over a UN worker in Fiji with Covid-19 who was allowed into New Zealand.

Late on Friday, Bloomfield sent in an apology to the Health Select Committee for failing to remember a text exchange he had with Chris Seed, the head of the Ministry of Foreign Affairs and Trade, about the worker.

The worker had been allowed into New Zealand from the Covid hot spot of Fiji. National had questioned the degree to which former PM and former UNDP head Helen Clark was involved in that decision.

Bloomfield had last week told the committee he had no direct contact with MFAT about the decision, but on Friday released a series of texts with Seed which Bloomfield said he had later recalled.

On Newshub this morning, Collins said she hesitated to criticise a public servant, but while Bloomfield was "good at standing up and talking about Covid … I just think that Ashley Bloomfield is probably a one-trick pony."

She stopped short of saying he should resign. "But I think he does need to do an awful lot to justify his position and the deification that has occurred," she said.

"Look, he was very good at standing up and talking to people, but when we were told by this Government - and he was standing there with it - that there is one source of truth, that was clearly entirely false."

National's Covid-19 spokesman Chris Bishop has put in a request for Bloomfield to front to the committee again – the committee will decide on that on Wednesday.

Bishop has questioned whether Bloomfield had misled the committee by saying the decision was made on clinical grounds.

However, Labour has a majority on the committee and can easily refuse it.

The text messages showed Seed telling Bloomfield that Clark had talked with both himself and Foreign Minister Nanaia Mahuta about the transfer.

Seed said that his ministry was "doing the right thing and staying well away".

Bloomfield replied saying "we're all over it. I think we will get resolution".

This was followed by a text saying the issue was "[a]ll sorted".

Collins has questioned how much influence Clark had, and whether it was appropriate.

Clark has not commented on the matter.