Australian police say an email that challenged Prime Minister Kevin Rudd's honesty and prompted calls for his resignation appears to be a forgery.
A fraud investigation began over the weekend when newspapers published an email that purported to be from a Rudd adviser to Treasury official Godwin Grech on behalf of the Prime Minister's friend, car dealer John Grant.
Police say detectives examined computers at the Canberra home of Mr Grech and at Treasury offices today in their hunt for the email.
Police say preliminary results indicate the email "has been created by a person or persons other than the purported author of the email."
The email was purportedly a request by a Rudd staffer in February for Treasury officials to give priority to Mr Grant's credit request.
Treasurer Wayne Swan said Mr Grant's request for government credit was treated no differently than that of any other car dealer as their usual sources of credit to buy cars dried up.
"I regard this as part of the smear campaign that has been conducted against the prime minister and myself by the leader of the opposition, and it's time for him to put up (evidence) or shut up and resign," Mr Swan told Nine Network television.
Mr Grant, who gave Mr Rudd a second-hand pick-up truck to use for campaigning and once sold Mr Swan a car, never received a loan from a two billion Australian dollar government fund set up as a last resort for car dealers struggling to access credit.
Mr Rudd told Parliament this month that no one in his office made any representation to the Treasury, which runs the fund, on Mr Grant's behalf.
But the fund manager, Mr Grech, told a Senate inquiry on Friday that he recalled being first alerted to Mr Grant's case by an email from Mr Rudd's office.
Mr Grech said he could find no record of such an email and conceded that his recollection could be wrong.
Mr Rudd then ordered the government inquiry into claims that his office corresponded with the Treasury on Mr Grant's behalf.