Emily Thornberry has denied allegations that she reffered to the constituents of the former Labour stronghold of Don Valley as “stupid”

Labour’s efforts to rebuild itself after the “disaster” of the party’s worst election result since 1935 descended into recrimination and rancour today.

As John McDonnell, the shadow treasurer, tried to frame the race for Jeremy Corbyn’s successor, one of those considered a front runner for the job, the shadow foreign secretary Emily Thornberry, was at war with a fellow Labour MP, accusing her of spreading a “total and utter lie”.

Former minister Caroline Flint, who lost her seat in the stronghold of Don Valley during the catastrophic election for Labour, claimed Ms Thornberry had told a colleague: “I’m glad my constituents aren’t as stupid as yours”.

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Ms Thornberry, the re-elected MP for Islington South & Finsbury, forcefully rejected the allegation. “The quote Caroline attributed