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Broadcaster Paul Holmes will be questioned by his Newstalk ZB boss on Monday over allegations that he struck an agreement with the National Party not to feature an American billionaire backer on his radio show.
Nicky Hager's book The Hollow Men claims Holmes agreed in July 2005 - two months before the election - not to have Julian Robertson on the top-rating breakfast show.
Labour had alleged that Mr Robertson had been contributing to National's election war chest.
The book says it was not known if Mr Robertson ever made a donation, but there was evidence he actively tried to help the National Party - such as by introducing Don Brash to two campaign strategists with links to the US Republican Party.
The book quotes an email from Brash's then chief-of-staff, Richard Long, to campaign director Steven Joyce, Murray McCully and Brash. "Paul Holmes wanted to get Julian," Long wrote, "but I said we would prefer to downplay that side of it and up-play our statement of today about concentrating on the issues and policy rollout. Paul accepted that."
The book also claims Holmes gave media training to Brash in the final week of the election campaign.
Newstalk ZB manager Bill Francis said he did not know if Holmes had struck an agreement with National.
