Jeremy Corbyn is not up to the job of being Opposition leader, former shadow Chancellor Alan Johnson has said. Mr Johnson added fuel to the fire of Labour’s infighting on Saturday morning, telling BBC Radio 4’s Today programme that “many of my colleagues” were sceptical of the leader’s abilities.

Mr Corbyn last night concluded the appointment of a new shadow Cabinet, promoting moderate Jon Ashworth to shadow Health Secretary and giving back posts to some MPs who resigned in June.

The rebuilding of the top team comes around two weeks after Mr Corbyn was re-elected as Labour leader at the start of the party’s conference in Liverpool. He won with an increased majority despite constant attacks from opponents within Labour and a sustained battering from the press.

Asked whether he thought Mr Corbyn was not up to the job, the Mr Johnson, a New Labour figure, told the programme: “Me, and many of my colleagues” think so. “Perhaps he'll prove me wrong.”

The shadow Foreign Secretary Emily Thornberry, however, robustly defending Mr Corbyn’s record. “The problem is that on the one hand people criticise, and have been criticising, Jeremy for being weak, for taking too long on his reshuffles, taking a couple of days, and yet when when he decides that he will do a reshuffle that he needs to do in order to fill vacancies and in order to reach out, people then criticise him for being too decisive and too strong,” she said.

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The row comes after a letter sent to all Labour MPs from Parliamentary Labout Party chair John Cryer. He said in the letter that talks regarding the reintroduction of elections to the shadow Cabinet had not been constructively engaged with by the leadership.