In July 2019, in the week Boris Johnson became Prime Minister, Campbell penned a 3,500 word open letter to Jeremy Corbyn saying he no longer wished to be re-admitted to the party, despite legal advice saying he would win a court case against his expulsion. He called on Corbyn to step down and cited his "failure" on Brexit, antisemitism, broader policy and "above all the failure to develop and execute a strategy". The story was broken in "The Guardian" and the full letter published in "The New European". Corbyn said he was "disappointed", prompting Campbell to ask why he had been expelled.