Todd Barclay was accused of secretly recording the conversations of a staffer.

Former National Party MP Todd Barclay will not be prosecuted by police after he once again refused to speak to them.

Police reopened an investigation into allegations Barclay, the former MP for Clutha-Southland, illegally recorded a staff-member after it emerged in June that former prime minister Bill English had been a key witness in the case.

Barclay was accused of secretly recording the conversations of his staffer Glenys Dickson. It is illegal to record a conversation you are not a part of in New Zealand.

NZ POLICE Then finance minister Bill English was interviewed by police in Southland about Todd Barclay's recording of his staffer.

Police have now closed the case as they have insufficient evidence. No warrants were executed and Barclay again refused to be interviewed.

READ MORE: Listen: Bill English's police statement on Todd Barclay

"After a thorough review of all information available to us, including legal advice both internal and from Crown Law, plus consideration of the Solicitor General's prosecution guidelines, police has (sic) determined that there is no change to the outcome of the original investigation," Assistant Commissioner (Investigations) Richard Chambers said.

Police rejected criticisms of the initial investigation and any claim that witnesses had been coerced.

"We are aware that the original investigation has been subject to some criticism," Chambers said.

"While we recognise the strong interest in this matter, the foundation of any decision to seek warrants or to prosecute is always the evidence available to us."

"Speculation, hearsay and third party information does not in itself constitute such evidence."

Barclay stood down at the election and has moved to London. Other than some brief press statements, he had refused to talk to media since announcing he would stand down.

The case gained new prominence when Newsroom revealed in June that English told police that Barclay himself had told him of a recording.

"I had a conversation with him regarding Glenys Dickson leaving his office and he said to me that he had recordings of her criticising him," English told Detective Superintendent Peter Read in the interview.

A spokesman for English refused to comment on whether it was appropriate for an MP to refuse to speak to police.

"As Mr English has always said, this is a matter for police. He has nothing further to add."