The Australian Federal Police (AFP) has confirmed it was making enquiries about regular travel and cash transfers to the Philippines by Queensland MP George Christensen for 12 months.

Key points: George Christensen has dismissed the referral to police as an attempt to smear his reputation

George Christensen has dismissed the referral to police as an attempt to smear his reputation AFP Commissioner Andrew Colvin told the Senate hearing that senior members of the Government were briefed

AFP Commissioner Andrew Colvin told the Senate hearing that senior members of the Government were briefed Mr Colvin said there was no evidence of any wrongdoing by Mr Christensen

The AFP told a Senate estimates hearing that inquiries began in late 2017, at least a year before Mr Christensen revealed he was the subject of a referral to police.

Mr Christensen has dismissed those referrals and suggestions he sent money to foreign bank accounts as an attempt to smear his reputation, given the country is known for prostitution and drugs.

Senior members of the Government, including former prime minister Malcolm Turnbull, former deputy prime minister Barnaby Joyce and Home Affairs Minister Peter Dutton, were all briefed by police at different times.

Nationals leader Michael McCormack was also told about the investigation when he took over leadership of the party.

"We were concerned that the information that we were evaluating was becoming known," AFP Commissioner Andrew Colvin told the hearing.

"I believe it was appropriate for [Deputy Prime Minister McCormack], because of the particular circumstances with the Deputy Prime Minister, to brief him."

The AFP told estimates that there was no evidence of wrongdoing by Mr Christensen.

Andrew Colvin told a Senate estimates hearing there was no evidence of wrongdoing. ( ABC News: Matt Roberts )

Police officials also said the Nationals MP has repeatedly described allegations against him as an attempt to smear his reputation.

Last week, when News Corp Australia published his travel records in the region, Mr Christensen said it was part of a "putrid" smear campaign against him.

"This whole matter is vile and defamatory," Mr Christensen wrote.

"I've asked myself why I've been the subject of such a vile and hateful smear campaign and I can only think it is because I stood up for my electorate against the powers that be, or rather, that were, on too many occasions.

"They now want revenge and have sided with Labor in this smear campaign to try and get that revenge.

"No doubt they will still throw mud from the sidelines without putting their name to their allegations, because the people involved in this smear campaign are so gutless, in fact they are the lowest of the low to stoop to such actions as they have."