The number of inmates sharing cells at Lewes prison designed for only one person has risen sevenfold in four years.

Almost 28 per cent of the overcrowded category B jail's 535 inmates are forced to double-up in single cells, Lewes MP Norman Baker has discovered.

A parliamentary question by Mr Baker also revealed the prison is five officers short of the amount required by Home Office guidelines. In March 2001, the prison had 445 prisoners, with only four per cent sharing single sells.

Liberal Democrat Mr Baker said: "Over a quarter of all prisoners are now housed in sub-standard conditions and there are insufficient prison officers to cope with the growing prison population.

"I am disappointed to see the situation with overcrowding at Lewes prison has got so much worse in such a short space of time.

"I visit the prison on a regular basis and am sure the excellent staff there do all they can to make the best use of the resources available to them.

"But there is a limit to what they can do if the Government continues to fail to address the central problem of overcrowding."

Lewes prison has 50 inmates more than its official capacity of 485.

Mr Baker added: "Under this Government the prison population has grown by almost 25 per cent but putting more and more people in prison is not winning the fight against crime.

"What we need to see is better use of tough, supervised community work for low-level, non-violent offenders which acts not only as a punishment but also equips them with skills they can use in the future and helps pay back their debt to the local communities they harmed."

In January the Chief Inspector of Prisons Anne Owers said Lewes had improved, despite the fact the Prison Service Annual Report last year said more than a quarter of inmates were held in overcrowded conditions.

This was still less than the target of 29 per cent.

The jail exceeded targets for the number of inmates who gained basic skills awards and started and completed drug treatment programmes.

The percentage of inmates who tested positive in mandatory drug tests was 11.48 per cent - 3.82 per cent lower than its target.