Whetstone contested the seat of Chaffey at the 2010 election for the Liberal Party, receiving a 20-point two-candidate swing from incumbent
Nationals MP
Karlene Maywald, to finish with 53.8 percent of the
two-candidate vote. The SA Nationals did not contest the
2014 election, which saw Whetstone win 75.1 percent of the two-party vote. Between June 2014 until the state election, Whetstone was the Shadow Minister for Trade and Investment, as well as being the Shadow Minister for Recreation, Sport and Racing from 2014 to 2017. In July 2020, Whetstone admitted to wrongly claiming travel expenses on 90 occasions over six years, including several claims for accommodation in Adelaide at the same time as he was undertaking international or interstate travel, in what Premier
Steven Marshall described as "extraordinarily disappointing" behaviour. As a result, Whetstone resigned from the
Marshall ministry on 26 July 2020. Whetstone repaid approximately $7,000 attributed to diary-keeping errors, and on 15 October 2020 was cleared of further investigation. Then-South Australian Independent Commissioner Against Corruption
Ann Vanstone explained that "the information provided so far does not reveal evidence of misconduct" and, as a result, had "decided not to widen those inquiries to other Members of Parliament." On 6 January 2023, Whetstone resigned as Shadow Minister for Road Safety after accumulating too many demerit points due to unspecified traffic offences, resulting in the loss of his license. Shortly following the incident, then-
Leader of the Opposition David Speirs appointed Whetstone as Shadow Minister for Trade and Investment, citing his experience and performance within the shadow ministry. Following
Vincent Tarzia's appointment as Opposition Leader in August 2024, Whetstone was given responsibility over the Industry, Recreation and Racing, and Emergency Services portfolios. He was also later appointed Shadow Minister for Social Services. ==References==