Former prime minister Tony Abbott has ignored repeated peace offerings by senior colleagues Julie Bishop and Christopher Pyne since his downfall as leader, a new book claims, in further signs of damaging disunity within the government just months out from a federal election.

The book by political commentator Niki Savva, The Road to Ruin, How Tony Abbott and Peta Credlin destroyed their own government, also alleges Mr Abbott slapped the buttocks of his chief of staff Peta Credlin, not realising a minister witnessed the behaviour. Fairfax Media has independently verified this account.

Mr Abbott and Ms Credlin both deny any romantic involvement. They have accused Savva of unethical journalism, complaining she did not put any claims to them before publishing.

There have been growing signs that the relationship between Mr Abbott and Prime Minister Malcolm Turnbull is deteriorating, including last week when Mr Abbott said he was "flabbergasted" by what he saw as a late delivery timeline for a future submarine fleet.