UPDATED 6:02pm: The office of the Ombudsmen is to look into the police decision to publicly withhold all information passed on to police about an investigation into former National MP Mike Sabin.

The Soap Box: Call for Sabin disclosure

In February, police cited prejudice of the law as among their reasons for not disclosing when - or if - the Prime Minister and Minister of Police were briefed about the case.

Now the Ombudsman, following a formal complaint from our political staff, have announced they are looking into the decision police made.

The police commissioner has been requested to provide chief ombudsman Dame Beverley Wakem relevant information and a report on the decision they made.

John Key has told the media he absolutely supports the Ombudsman's investigation and he's confident it won't turn up any evidence that contradicts his previous positions on the matter.

"I stand by the statements I publicly made on that, which was the first I was advised was the first of December, I think it was, last year."

Labour Leader Andrew Little admits he sees no reason why police can't say when they briefed the Government about their investigation.

"The issue about what time the relevant government ministers knew a relevant matter such as this is, while it might be embarassing for the government, shouldn't be a reason to hold that information from the public."

New Zealand First leader Winston Peters believes it'll show the Government did know of the matter before last year's election - something the Prime Minister's previously denied.

"We thought we had a $1 million byelection up north in circumstances where the government did not take the steps it should've taken and that's what we're going to find out - did they think they could tough it out?"