Nationals MPs say they are happy for controversial MP George Christensen to remain their party whip despite him again publicly toying with breaking away from the government.

Mr Christensen last week penned a letter to Prime Minister Malcolm Turnbull in which he said his support for the government could not be guaranteed without action on a local sugar industry stoush in his north Queensland electorate. Mr Christensen did not send the letter but provided details of its content to the media.

In it he said his support for the government was contingent on Mr Turnbull announcing a mandatory code of conduct for the sugar industry by March 1, with penalties.

Mr Christensen's repeated public doubts about being a member of the Coalition and threats to cross the floor have raised questions about his role as Chief Nationals Whip, a position that puts him in charge of enforcing party discipline.