National MP Paul Hutchison was caught reading while driving, and now his colleagues are being warned off the practice.

Hunua MP Paul Hutchison had papers spread across his steering wheel and an astonished motorist who reported him to the media said it looked like he was practising a speech.

Janice Barr from Ohaupo, near Hamilton, said the four-wheel-drive vehicle had Dr Hutchison's name and National Party colours on it.

Dr Hutchison said today he was sorry.

Acting Prime Minister Bill English spoke to him this morning and said the MP was severely embarrassed and it was to his credit that he had owned up.

"I'm actually going to remind caucus that Members of Parliament might be busy but they've still got to keep the rules of the road," Mr English said.

Transport Minister Steven Joyce also had the chance to talk with colleagues.

Dr Hutchison's actions were "very unwise" and "not a good look", he said.

"The Acting Prime Minister gave me the opportunity at caucus to remind caucus colleagues it's appropriate that we set an example with the road rules and I know that Dr Hutchison has taken that view as well."

There had been a "renewed commitment" from Dr Hutchison and other MPs to follow the rules, Mr Joyce said.

"Driving while distracted is against the road rules right now and it's a no-no."

Dr Hutchison said he had been distracted at the time by a large workload and was not concentrating, he said.

"It is very embarrassing.

"It was very unwise, I was doing the wrong thing and I think the lady was absolutely right in dobbing me in."