Key Points:

The police have broadened their inquiry into Don Brash's "stolen" emails into suspected burglary after a complaint by Auckland businesswoman Diane Foreman.

She has complained to police about the Nicky Hager book The Hollow Men and questioned how information that was not in any email came to be in the book.

Mrs Foreman confirmed last night that she had spoken to the police.

"I think it is better that I don't comment on any of this but I am more than happy to confirm that I have had discussions with the police in regard to the Nicky Hager book."

She was highly critical of The Hollow Men. "There are things in the book that are absolutely false. It's nasty, it's grotty, it's horrible."

She believed that the police investigation had been widened beyond the issue of emails.

Mrs Foreman, vice-chairwoman of the Business Roundtable, is mentioned many times in the Hager book as a friend, adviser and donor. She was also the "other woman" at the centre of Dr Brash's marriage crisis in September.

The book is based largely but not entirely on Dr Brash's emails. It also quotes emails that were sent between his advisers but not copied to him, faxes that were not emailed, and appointment diaries.

Hager says six National Party sources supplied him with material before last year's election.

But since the book's publication National has become more concerned that it may have been the subject of a criminal conspiracy by political opponents.

The private rubbish bins of National leader John Key were ransacked by men thought to be private detectives.

The police officer leading the inquiry, Detective Inspector Harry Quinn, would not say whether the investigation had been broadened beyond emails.

However, yesterday he briefed Dr Brash and National's parliamentary chief of staff, Wayne Eagleson.

Mr Eagleson said the police shared some of the intelligence they had received on the matter.

He was not sure the investigation had been formally widened but said "the police are certainly not just looking at emails".

The Hollow Men lays bare much of the thinking behind Dr Brash's leadership and the 2005 campaign.

Meanwhile, in further fallout from the book, historian, newspaper columnist and former Labour Party minister Michael Bassett has parted company with the Dominion Post.

The fact that Dr Brash had sought and received advice from Dr Bassett on his Orewa speeches was cited in a letter editor Tim Pankhurst sent Dr Bassett terminating his column.

"I believe this should have been declared and both you and the Dominion Post are exposed to duplicity," Mr Pankhurst wrote.

Dr Bassett, in his response to the "ungracious" letter published on his website, says: "The suggestion that I wrote either of Don Brash's Orewa speeches is preposterous.

"I provided the information when asked, and I suggested where further material might be gleaned. Soon after that speech Dr Brash told the press about those who had helped check its accuracy, mentioning my name. Nobody, least of all an editor, has any excuse for being unaware of this fact. Suggestions of duplicity are therefore completely wrong."