A former top prosecutor says he personally warned Boris Johnson about the risk posed by freeing terrorists who had not been deradicalised, but was told there was “no money”.

The hugely damaging claim came as the solicitor for the London Bridge attacker revealed he had asked for help to turn away from terrorism while in prison, but was not given any. As anger grew over the early release of Usman Khan, Jeremy Corbyn branded the attack he was able to carry out “a complete disaster”, saying: “There has got to be a very full investigation.” Visiting London Bridge, the prime minister attempted to deflect blame, saying: “I’ve argued that when people are sentenced to a certain number of years in prison they should serve every year of that sentence.” But the focus switched to efforts made to deradicalise prisoners when Nazir Afzal, the former chief prosecutor for North West England, intervened by revealing his private conversation with Mr Johnson. He said he had raised the problem of terrorists being released “whilst ostensibly rehabilitated but still radicalised” in many government meetings, before raising it with Mr Johnson in June 2016. “He asked me what keeps me awake at night and I told him it was this issue,” Mr Afzal said. “When he wanted to know what to do about it, I told him it was more resources for one-to-one deradicalisation.

“Back then, he hadn’t found the ‘money tree’ so he frustratingly said there was no money.” The atrocity committed by Khan – who killed two people, before being shot dead by police on Friday – has become a major general election controversy, with questions also asked about the apparent failure to monitor him.

Meanwhile, the Conservative campaign lead has been halved in just one week, putting the UK in “hung parliament territory”, an exclusive poll for The Independent showed. Further questions were raised when the Parole Board said it had no involvement when Khan left prison last December, saying he “appears to have been released automatically on licence”. Chris Phillips, a former head of the UK National Counter Terrorism Security Office, warned the criminal justice system was “playing Russian roulette” with the lives of the public.