The prime minister is considering blocking PC Andrew Harper’s killers from being released early from prison, it has been reported, after he previously suggested he would not be able to keep them behind bars. Prime minister Andy Burnham is prepared to “explore every option” to keep them both in prison, a government source told the Telegraph on Friday. The government has so far resisted pressure to exempt the two killers from its early release scheme, which will start in October in a bid to tackle prison overcrowding. Around 5,000 people are expected to be released early under the scheme, down from 6,000 after the exemptions were announced as part of an urgent review. The early release changes are part of the Sentencing Act, which passed earlier this year and cut the minimum amount of time many offenders would have to spend in prison.