OTTAWA - Stephen Harper's office says it's "difficult to imagine" the prime minister would have any relevant information to share in the trial of Sen. Mike Duffy.

Spokesman Jason MacDonald says in an email that the PMO has responded "fully and freely" to requests for assistance from RCMP investigators.

He adds the Mounties have made it clear they don't believe Harper has any knowledge of Duffy's alleged wrongdoing and that there would be no reason for the prime minister to be involved should Duffy's defence team attempt to have him testify.

The RCMP announced last week it was charging Duffy with 31 criminal counts related to his expense claims, accusing him of misspending more than $200,000.

The charges stem from the disgraced senator's housing and travel expenses, and a $90,000 payment from Nigel Wright, the former chief of staff to Harper.

Duffy has denied any criminal wrongdoing.