Taito Phillip Field could be on leave for a long time.
Estimates around Parliament of the time it will take the police to complete their inquiry into allegations against the Labour MP range from six months upwards.
And National's deputy leader, Gerry Brownlee, thinks it will take longer than eitherthe David Benson-Pope tennis ball inquiry or the investigation into Prime Minister Helen Clark's speeding motorcade.
The tennis ball inquiry was referred to the police on May 18 last year and the police report was released on December 5 - just under seven months later.
Police ordered the inquiry into the motorcade on July 20 and reported on November 12, just under four months later.
The inquiry into allegation against Mr Field was announced last Thursday, and the MP was sent home on leave on that day.
He has relinquished all his duties as an MP, although Labour retains his vote which will be cast by proxy in Parliament.
The inquiry appears to be much more complex than either the tennis ball or motorcade investigations.
The police made their decision after sifting through the report by Noel Ingram, QC, who investigated Mr Field's dealings with Asian immigrants he helped gain visas.
They are also going to look at new allegations, which include claims he took money from his constituents when he helped them and ordered a birth certificate to be altered for a visa application.
They are understood to be investigating whether any of his dealings constitute bribery under the Crimes Act, or possibly fraud - relating to the altering of a document.
Mr Brownlee told NZPA it appeared to be a much more difficult task than the tennis ball or motorcade inquiries.
"They've got all sorts of difficulties with this," he said.
"There's a very significant language barrier, particularly with the Thai community.
"That's going to be a factor, and then you've got people living offshore so there will be jurisdictional issues."
Mr Brownlee also pointed to "multi-layered possible transgressions" the police will be considering.
While he is on leave Mr Field is not expected to come anywhere near Parliament, and he won't have anything to do outside it.
He will continue collecting his salary and allowances, worth about $150,000 a year.
