UK Parliament

Whitfield was named as the official Labour Party candidate for the East Lothian constituency at the 2017 UK general election,^[10][11] where he unseated the sitting Scottish National Party MP, George Kerevan.^[9]

Whitfield was an active opponent of Brexit and a strong supporter of a second referendum, referred to as a "People's Vote".^[12][13] He supported the official recognition of non-binary people in official government documentation.^[14] He was one of 216 general election candidates to pledge support for the Israel Election Pledge.^[15] Whitfield attracted controversy in a debate on the abuse of MPs when he claimed that "now is the time to ban anonymous social media accounts". He claimed that he was echoing similar remarks from SNP MEP Alyn Smith.^[16]

In June 2018, Whitfield led an adjournment debate on the challenges faced by people with 'hidden' disabilities, particularly in relation to the use of accessible toilets and cited the Grace's Sign campaign run by a young constituent, Grace Warnock.^[17] In June 2019, he led a further backbench debate on invisible disabilities and accessibility challenges, including the new Any Disability Sign.^[18] Whitfield was a strong critic of the rollout of Universal Credit and was one of the first Labour MPs to call for the new benefit to be replaced entirely.^[19] In October 2018, he attracted widespread praise after leading a Commons debate on World Menopause Day.^[20]

Following the announcement that the US would impose tariffs on single malt Scotch whisky from 18 October 2019, Whitfield took a leading role in efforts to encourage the UK Government to persuade US counterparts to reconsider the move and co-ordinated a letter to the US Ambassador.^[21] Whitfield was a member of several All-Party Parliamentary Groups, including the Timber Industries APPG, which he chaired.^[22] He was also a member of the Commons' Science and Technology Select Committee.^[23]

Whitfield was the Co-Chair of Anas Sarwar's unsuccessful 2017 Scottish Labour leadership campaign.^[24] He supported MP Ian Murray's UK Labour deputy leadership campaign, MSP Jackie Baillie's Scottish Labour deputy leadership campaign, and Anas Sarwar's successful 2021 Scottish Labour leadership campaign.

He lost his seat at the 2019 general election to the SNP candidate, Kenny MacAskill.^[25] He later became a supporter and executive committee member for the organisation Scientists for Labour, providing advice and input to Sir Keir Starmer's office on the COVID-19 pandemic.^[26]

Scottish Parliament

Whitfield stood for election to the Scottish Parliament in the East Lothian constituency^[27] and the South Scotland regional list at the 2021 Scottish Parliament election.^[28]

At the election, Whitfield finished in a close second place behind the SNP, with 16,789 votes and a share of 36.6%, but was elected on the South Scotland list vote.^[29]