Anna Soubry has accused Chuka Umunna of failing to “step up” to become leader of breakaway party Change UK.

The current leader said her former colleague, who joined the Liberal Democrats last month, had a ”history of not stepping up” and revealed that the pair, previously close allies, had not spoken for almost two months.

Mr Umunna had been expected to lead the breakaway group of former Tory and Labour MPs but instead Heidi Allen, a former Conservative, was chosen as interim leader.

Ms Allen quickly caused a stir and was criticised by colleagues after suggesting that pro-EU voters should back the Liberal Democrats rather than her own party.

Change UK split following a disastrous showing in the European elections in May, with Mr Umunna eventually joining the Liberal Democrats and Ms Allen and four others returning to sit as independents.

Ms Soubry leads the remaining five Change UK MPs.

Asked what had gone wrong during the party’s first few months, she told ITV News’s Acting Prime Minister podcast: “We made some terrible mistakes over leadership and I can tell you now that the problem was was that Chuka wouldn’t step up to it.

“If Chuka had stepped up to it he would have been our leader, it was certainly... well I always assumed it was absolutely going to happen.”

She accused Mr Umunna of having a “history of not stepping up”.

She said: “[It’s] very sad because to me he was absolutely the future for our country. I genuinely believe that, I wouldn’t have left my party if I hadn’t believed that.”

She added: “He should have been our leader and he wasn’t and then after the EU elections, which were a terrific blow of course ... you don’t give up at the first hurdle.”

Ms Soubry claimed her former colleague had made “a terrible mistake” by joining the Liberal Democrats – a decision she said he had not informed her of. The pair have exchanged emails in recent weeks but have not spoken in person since mid-May.

She said: “I think he made a terrible mistake. I was genuinely really sad about that.

“For me it personally hurt, it really did hurt. I thought he was my big buddy. He was a major part of why I left the Tory party – to start something new with him as the leader. I don’t want to be the bloody leader.”

Which MPs defected to form Change UK? Show all 12 1 /12 Which MPs defected to form Change UK? Which MPs defected to form Change UK? Change UK Details on the individual MPs are in the following photos Reuters Which MPs defected to form Change UK? Heidi Allen Anti-Brexit MP for South Cambridgeshire resigned from the Conservative party on February 20 PA Which MPs defected to form Change UK? Chuka Umunna MP for Streatham since 2010 and prominent People's Vote supporter PA Which MPs defected to form Change UK? Anna Soubry The prominent anti-Brexit MP for Broxtowe resigned from the Conservative party on February 20 PA Which MPs defected to form Change UK? Luciana Berger MP for Liverpool Wavertree since 2010, resigned from the Labour Party over bullying and anti-semitism PA Which MPs defected to form Change UK? Sarah Wollaston Anti-Brexit MP for Totnes resigned from the Conservative party on February 20 PA Which MPs defected to form Change UK? Joan Ryan MP for Enfield North resigned from the Labour party on February 19 citing its tolerance of a "culture of anti-Jewish racism" PA Which MPs defected to form Change UK? Ann Coffey MP for Stockport since 1992 Chris McAndrew / UK Parliament Which MPs defected to form Change UK? Gavin Shuker MP for Luton South since 2010 Getty Which MPs defected to form Change UK? Chris Leslie MP for Nottingham East since 2010 PA Which MPs defected to form Change UK? Mike Gapes MP for Ilford South since 1992 PA Which MPs defected to form Change UK? Angela Smith MP for Penistone and Stocksbridge since 2010

She added: “I genuinely believe that Chuka Umunna should be prime minister of our country and had just what we were needing to be a great prime minister. I genuinely believe that.”

Ms Soubry also said she would “certainly not” give Boris Johnson a cabinet position if she was prime minister.

She said: “He couldn’t even be trusted to clean the loos. I’m being really serious. He was an appalling foreign secretary. He was the worst foreign secretary our country has had in living memory.