“Labour will contest the next election on changing Britain’s electoral system to proportional representation.”

• Propositions: 3; evidence items: 11; pipeline_outcome=ok
• [supporting] An official UK government publication records a speech delivered by 'Prime Minister Andy Burnham' at the UN General Assembly on 22 September 2026, in which he refers to himself as 'the new British Prime Minister'.
• [supporting] BBC News reports that Keir Starmer delivered his final address as Prime Minister and that Andy Burnham succeeded him, with Starmer announcing his resignation effective 22 June 2026, four days after Burnham won a Westminster seat.

The claim is true because proposition p1 is assessed TRUE (confidence 1.0) based on official UK government records e1 and e6 that explicitly name Andy Burnham as Prime Minister in September 2026, with attribution evidence e10 confirming his current role; proposition p2 is assessed TRUE (confidence 1.0) as e6 and e10 give his start date of 20 July 2026, corroborated by BBC News e2 reporting the transition from Keir Starmer; proposition p3 is assessed TRUE (confidence 1.0) because New York Post articles e3 and e8 refer to him as Prime Minister and the gov.uk page e11 independently confirms his holding the office. Non‑corroborating evidence e4, e5, e7, and e9 do not contradict the finding but lack specific identification of the Prime Minister or details about the transition. Limitations: Relies primarily on UK government websites (gov.uk) that could be updated or edited after the fact check, limiting long‑term certainty.; The start date of 20 July 2026 rests on official biographies and a BBC news report; there is no independent primary source (e.g., a formal gazette) verifying the exact transition moment.; Attribution evidence includes tabloid/New York Post articles, which are treated as attribution rather than independent verification.; The fact check does not address any potential changes to the premiership after September 2026, as no evidence beyond that period was examined.