Police have reopened an investigation into allegations that National MP Todd Barclay secretly recorded a staff member.

Photo: RNZ / Ian Telfer

Mr Barclay will not stand again at this year's general election after the scandal involving a former electorate staff member and a recording she told police the MP had made of her in the Gore office.

The case was closed last year when police concluded they had insufficient evidence to prosecute Mr Barclay. The Clutha-Southland MP had declined to be interviewed as part of the investigation.

Assistant Commissioner of Investigations Richard Chambers said today police would consider a range of new information and comment that has come to light over the past week.

At the weekend Prime Minister Bill English said Mr Barclay offered to play the recording to him when they first spoke about it, but that he did not think it was "appropriate" to take up the offer.

Mr English said he would cooperate with the police investigation, and has urged his MP to do the same.

Mr Chambers said police had started speaking to a number of individuals who might have relevant information, and new evidence that was gathered would be carefully considered to determine what, if any, impact it would have on the outcome of the original investigation.

A senior detective would oversee the investigation but police were unable to put a timeframe on how long it might take.

The Todd Barclay story dominated the National Party conference over the weekend, with Mr English coming under intense scrutiny over his own response.