The Government will not be able to build its way out of the prison crisis, Jack Straw suggested yesterday. He indicated that the only way the pressure could be relieved was by sending fewer people to jail and using more noncustodial sentences.

In an interview with The Times, his first since becoming Justice Secretary and Lord Chancellor, Mr Straw called for a “national conversation” about the use of prison. He also spoke of the need to make community sentences more effective to build confidence and trust in noncustodial sentences.

Even if he could click his fingers “and magic an extra 10,000 places” they would still have to have the same debate about the use of prison, he said. His call came amid growing concern in the Prison Service that the recently implemented early-release scheme may not be enough to prevent another crisis of inmate numbers in the autumn.

During the interview Mr Straw sought to reassure the judiciary by emphasising that he was “wholly opposed” to giving MPs the power to approve the appointment of judges. He would consult about the suggestions for making judicial appointments more accountable to Parliament that were set out in last week’s Green Paper on constitutional reform.

Mr Straw said that there would be wide public involvement, including the use of citizens’ juries, about proposals for a bill of rights and responsibilities and a possible written constitution. He opposes a citizens’ convention or assembly to agree changes. The aim is to strengthen trust in Parliament and public engagement, especially young people’s confidence in the political process.

He ferociously attacked Conservative proposals to prevent Scottish and Welsh MPs from voting in the Commons on laws applicable only to England. Such a move would wreck Parliament and the Union, he said.

The prison population stood at 79,453 last Friday but rose by 150 over the weekend. One prison source told The Times: “We are worried about the continuing upward trend. If this continues there will be another crisis with the jails full in the late summer or early autumn.”

The new Justice Secretary is ready to announce that 500 prison spaces are to be provided in existing jails and plans are under way to build two jails at Maghull, on Merseyside, and Bel-marsh, in southeast London, with a further 9,500 places by 2012.

But Mr Straw signalled a renewed government focus on finding alternatives to prison as a means of stabilising a jail population that has doubled in the past 30 years. The early-release scheme, in which prisoners serving between four weeks and four years are released 18 days early, had reduced the jail population by 1,500 at any one time. “I can’t say whether it will be a permanent feature,” he said. Mr Straw added: “The crucial thing here is how we improve everyone’s trust in noncustodial sentences. I want to work not only with magistrates and judges but with others as well as the public . . . [protecting] above all the interests of victims and communities.”

He also backed greater use of fines, and said that an investigation was under way into why, when the enforcement of fines had increased, their use by the courts had fallen.

Asked about judicial appointments, Mr Straw said he was “wholly opposed to the politicisation of the appointment process, which has happened in the US”. The quality and standing of the judiciary in Britain was high compared with many Western countries and “preserving that above all is my priority”. He added that he had no intention of moving on the issue without the broad consent of the senior judiciary.

He also tried to placate judges over their fears that the splitting of the Home Office into two, creating his department, would harm the courts and the legal aid budget.

He pointed out that his oath of office as Lord Chancellor required him to “provide resources for the efficient and effective support of the courts”. He would consider their call for “ring-fencing” the budget but “it is cash that ultimately matters”.

His predecessor, Lord Falconer of Thoroton, QC, admitted that the Government would be unable to build its way out of prison overcrowding. He said that the only long-term option was for fewer criminals to be sent to jail and that expanding the prison estate was not a workable long-term option.

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