The prime minister said three times it would not be right for him to comment on the investigation into his former parliamentary aide, Craig Williams.
Mr Williams, a Conservative candidate in the general election, has admitted a "huge error of judgement" in placing a bet on the date of the general election.
Speaking from the G7 summit in Italy, Rishi Sunak said it was “very disappointing news”. But asked whether Mr Williams had known the 4 July date when he placed his wager, the PM repeatedly declined to say any more while the Gambling Commission held an “independent" and "confidential" inquiry.
The other candidates standing in Montgomeryshire and Glyndwr are:
- Jeremy Brignell-Thorp, Green Party
- Oliver Lewis, Reform UK
- Glyn Preston, Liberal Democrat
- Elwyn Vaughan, Plaid Cymru
- Steve Witherden, Labour.