The official in charge of the OzCar scheme, Godwin Grech, has told a Senate inquiry he realised the "sensitivity and import" of his statement.

"My understanding (was) the initial contact that I had with respect to John Grant was from the prime minister's office," Mr Grech told the inquiry.

Treasury officials had previously said they'd been unable to locate representations from Prime Minister Kevin Rudd's office to Treasury regarding Mr Grant, who is a neighbour of Mr Rudd's.

Labor senators and fellow Treasury official David Martine spent more than 10 minutes trying to stop Mr Grech answering a question about whether Mr Grech had seen a document from Mr Rudd's office regarding Mr Grant.

Liberal senator Eric Abetz, who asked the question, said he accepted Treasury hadn't been able to find such a document, but that didn't mean one hadn't existed in the past.

When Mr Grech finally answered the question he was clearly emotional.

He prefaced his reply by saying no public servant should be placed in the position in which he found himself.

Mr Rudd has previously said neither he, nor his office, made representations on Mr Grant's behalf.

"Neither I, nor my office, have ever made any representations on his behalf," the prime minister told parliament earlier this month.

Senator Abetz told the inquiry a journalist had suggested to him that there'd been a communication from Mr Rudd's office to Mr Grech, which read as follows:

"The prime minister has asked if the car dealer financing vehicle is available to assist a Queensland dealership, John Grant Motors, who seems to have trouble getting finance.

"If you could follow up on this ASAP that would be very useful."

Opposition Leader Malcolm Turnbull was accused of bullying one of Mr Rudd's senior advisers earlier this week over the existence of the document.

The government released a file note from economic adviser Andrew Charlton on Friday, in which he alleged Mr Turnbull threatened him on Wednesday.

The opposition believes Mr Charlton wrote the document to Mr Grech.

"This whole OzCar issue will be very damaging for you," Mr Turnbull reportedly told Mr Charlton.

"Let me give you some friendly advice. You should not lie to protect your boss. You know and I know there is documentary evidence that you have lied."