Jeremy Corbyn has written a letter of apology to Labour supporters, saying “no matter how low our opponents went, we refused to join them in the gutter” but not acknowledging antisemitism.

The Labour leader’s letter, published in the Sunday Mirror, did not mention claims of Jew-hate among the list of reasons for the party suffering the worst electoral failure since 1935, despite Labour being only the second UK party after the far-right BNP to be investigated by the Equality and Human Rights Commission.

Mr Corbyn said: “We will learn the lessons of this defeat, above all by listening to those lifelong Labour voters who we’ve lost in working class communities.

“This party exists to represent them. We will earn their trust back... I remain proud of the campaign we fought.

“I’m proud that no matter how low our opponents went, we refused to join them in the gutter,” he wrote. “And I’m proud that our message was one of hope, rather than fear.”

The Labour leader repeated claims that Labour’s policies were “popular with votes” who “saw through a ferocious smear and fear campaign”, and that “the election was ultimately about Brexit” in the letter.

The letter comes as the Sunday Times reports that Corbyn intends to remain Labour leader until April 2020, sources close to him say, adding that it would take three months for a leadership contest and there is currently no deputy leader.