Wollaston initially supported the Vote Leave campaign during the 2016 referendum on European Union membership, stating in an article in "The Guardian" following David Cameron's renegotiation of membership terms in February 2016 that "the prime minister has returned with a threadbare deal that has highlighted our powerlessness to effect institutional change" and that "the balance of our national interest now lies outside the EU". However, she announced on 8 June 2016 that she would change sides to campaign for Britain to remain in the EU, claiming that Vote Leave's assertion that exiting the union would make available £350m a week for health spending "simply isn't true" and represented "post-truth politics". She also suggested that leaving the EU would harm the UK's economy, leading to a "Brexit penalty". Michael Deacon of "The Daily Telegraph" wrote her decision to switch sides had sparked a conspiracy theory among many Leave campaigners that she was a "government plant", while fellow Conservative MP and Eurosceptic Nadine Dorries said that Wollaston's change of opinion was "deliberately staged and political".