Prison governors have been warned that jails will be so overcrowded by the second week of July that they will struggle to accept any more inmates, plunging an incoming government into an immediate crisis. The heads of jails in England and Wales were informed by HM Prison and Probation Service officials earlier this month that data pointed to an “operational capacity breaking point” only days after the 4 July general election. The development signals a significant logistical headache for an incoming justice secretary. It is expected to trigger Operation Early Dawn, a crisis measure that allows offenders to be housed in police cells when jails are full, while other measures can prompt magistrates courts to delay cases. The measures are in addition to a temporary government scheme under which prisoners can be released up to 70 days early. Tom Wheatley, the president of the Prison Governors Association, said: “We understand that we will no longer be able to receive prisoners from court in the second to third week of July. It is not an exact science – but it is very soon after the election. “This position was projected some time ago. The outgoing government did not take the necessary action in a timely fashion to avoid this.” Wheatley said any attempt to cram further offenders into prisons beyond the operational capacity could be challenged in the courts. “If a new government arrives and says: ‘We want more people in,’ it would be challenged in court by the PGA because ministers would be placing our members at risk,” he said. Operation Early Dawn is a contingency measure that has been used for very short periods – usually no longer than a week – to manage immediate, localised, pressures on the prison estate. It steps up coordination between police stations, the Prison Service and the courts to make sure nobody is taken to the courts until the Prison Service can guarantee a space for them should they be remanded. According to the latest Ministry of Justice (MoJ) data, released on 14 June, the usable capacity in prisons across England and Wales was 88,815, while the population was 87,347. In May, Operation Early Dawn was trigged in London and north-east England before being rolled out across England after concerns over prison overcrowding. It meant that defendants in police custody remained there and were not transferred to magistrates courts for bail hearings in case there was no space in jail cells for those remanded into custody. During the same month, police were instructed to consider making fewer arrests because of the lack of space in prisons. In a further development, officials have drawn up plans to reduce the time served by prisoners from the current halfway point in their sentences to about 43%. Modelling shows this would be the most effective medium-term solution to the overcrowding crisis, generating thousands of spare places. It would replace the current ad hoc early release scheme of up to 70 days. The Conservative party has shelved its pledge to ensure that most sentences under 12 months should be suspended and served in the community, rather than in prison. The proposal formed part of the sentencing bill, which was introduced during the last session of parliament. The bill’s progress ground to a halt when a group of rightwing Tory MPs organised in opposition to the policy. The Conservative manifesto omitted any mention of the plan to scrap short prison sentences. It also fails to mention a second element of the sentencing bill, which would have lowered the prison population – a move to extend eligibility for early release under the home detention curfew scheme for people serving sentences of more than four years. Labour insiders said the party would force through planning permission for new prisons but have not said how it would deal with an immediate overcrowding crisis, saying they had not had access to government data but were aware that they faced a “brutal inheritance”. The party is widely expected to form the next government. Shabana Mahmood, Labour’s shadow justice secretary, said: “This is just the latest example of the chaos the Conservatives have created in our criminal justice system. “Not only are they releasing prisoners in secret, now they are deliberately delaying the delivery of justice. For months, the Conservatives have been operating under a cloak of darkness. They must now come clean about the true scale of the crisis on their watch.” The Conservative party has been approached for a comment. The MoJ declined to comment in line with purdah rules.