Increase of 1,000 prisoners in three weeks threatens more budget cuts Prison numbers have soared a further 407 in the last week. Photograph: Martin Godwin for the Guardian A rise of more than 1,000 in the prison population in England and Wales in the last three weeks is threatening to trigger a new round of justice budget cuts, a top Whitehall official has warned. The latest justice ministry figures published on Friday show that prison numbers have soared by a further 407 in the past week, taking the total population to 87,668 - 3,500 higher than at the same time last year. Sir Suma Chakrabarti, the justice ministry's permanent secretary, told MPs that the increase in prison numbers in the last three weeks was the biggest rise after the Christmas 'dip' for several years. He told the Commons public accounts committee that the rapidly rising costs of the prison population was "one of the biggest risks we face." Chakrabarti, speaking after a fortnight in which the jail population had risen by 300 a week, but before last week's figures, said that the department currently had the funds to meet the extra costs. But he went on to warn that "if that rate of rise continues we will have to revisit all the figures" in the budget fixed last October. The justice ministry is already facing a fierce parliamentary battle over implementing £350m of legal aid cuts and is pressing ahead with significant savings in the courts, prison and probation budgets. A deeper round of mid-year cuts triggered by the prison crisis would provoke an even bigger political headache for the justice secretary, Ken Clarke. The population figures published on Friday show that 87,688 are being held in a prison system with a "useable operational capacity" of 89,399, giving prison managers an "operating margin" of 1, 721 places. A further 2,701 prisoners have been released early on electronic tags under the home detention curfew scheme. A Ministry of Justice spokesperson said two new prisons - Oakwood next to Featherstone prison at Wolverhampton, and Thameside, next to the existing Belmarsh prison in east London - were due to open in April to provide more capacity. Juliet Lyon of the Prison Reform Trust said the current jail population was neither justifiable nor sustainable. "In the face of numbers rising at the shocking rate of the size of a small prison a week, for social and economic reasons the government must hold its nerve," she said. Instead of revising figures and trying to find scarce funds to pour down the prisons drain, money should be spent on cutting crime. This can be done by working intensively with the serious and violent offenders who should be in prison and for whom there are already sufficient places. She said reducing the unnecessary use of custodial remands, investing in treating drug and drink addictions and diverting many women and children and the mentally ill from jail would also help.