Malcolm Turnbull is set to divulge what he knew about a federal police probe into Nationals MP George Christensen's frequent travel to south-east Asia.

The Age, The Sydney Morning Herald and Nine News can reveal the former prime minister's memoir A Bigger Picture, due to be released in April, contains references to the year-long evaluation of Mr Christensen's time in the Philippines.

Nationals MP George Christensen spent 294 days in the Philippines over a four-year period. Credit:Alex Ellinghausen

According to sources who have seen draft versions of the book, Mr Turnbull is set to lift the lid on some of the high-level conversations held about the Queensland MP's regular overseas trips.

The revelations come as the Nationals MP continues to block information being released to the public about the police probe and an audit of his parliamentary expenses.