Opposition Leader Malcolm Turnbull has denied any coalition involvement with an email that purportedly shows Prime Minister Kevin Rudd sought a government loan for a car dealer friend.

The government has called on Mr Turnbull to put up or shut up in relation to an alleged email that indicates the prime minister sought help for Ipswich car dealer John Grant under the $2 billion OzCar vehicle financing scheme.

Mr Rudd has rejected claims that his office lobbied on behalf of Mr Grant.

Mr Turnbull said on Saturday that the coalition did not provide the email to the media or fabricate the email itself.

"I don't have a copy of the email," Mr Turnbull told reporters in Sydney on Saturday.

"The email was not provided to (the media) by anyone in the opposition."

He also said the coalition had nothing to do with the origin of the email.

"The email was not composed by anybody in the Liberal Party - it was not composed by anyone in the opposition.

"It was not provided to The Telegraph by anybody in the opposition."

On Saturday News Limited's The Daily Telegraph published emails it says were sent by Andrew Charlton, Mr Rudd's senior adviser, to Mr Grech.

A February 19 email from Mr Charlton to Mr Grant reads:

"Hi Godwin, the PM has asked if the car dealer financing vehicle is available to assist a Queensland dealership, John Grant Motors, who seems to be having trouble getting finance.

"If you can follow up on this asap that would be very useful. Happy to discuss. A."

In an alleged reply sent by Mr Grech on February 23 to Treasurer Wayne Swan and Department Liaison Officer (Economic) Andrew Thomas, Mr Grech reports on his progress.

"Andrew, as promised, I raised the case of John Grant with the CEO of Ford Credit, Greg Cohen, during my meeting with Ford Credit in Melbourne today.

"Cohen gave me an undertaking that Ford Credit will actively look at taking Grant on.

"John Grant called me earlier this afternoon (from Auckland) to say that Ford Credit had been in contact with him after my meeting."

An undated email, also allegedly sent by Mr Grech to Mr Swan and Mr Thomas, expresses concerns.

"Andrew, I told Grant to keep in touch and to let me know if Ford show concerns or resistance (I will not speak with Ford again on this unless it is absolutely necessary to push it through)," Mr Grech reportedly wrote.

"He also said that he wants to come to Canberra to meet me (and I assume you). Although I said nothing, I don't think that would be a good idea until this is settled. Godwin."

Mr Thomas thanked Mr Grech in a responding email.

"Great work," the email read.

"Just so you are aware, these emails are also going to the Treasurer's home fax. Cheers, Andrew.

Mr Turnbull has called on Mr Rudd and Mr Swan to justify their actions over links to Mr Grant or resign.

AAP