Jack Straw said he disagreed with the Prison Reform Trust report
Justice Secretary Jack Straw has defended conditions at two jails in Lancashire, after a report about prison overcrowding in England and Wales.
The Prison Reform Trust said two-thirds of jails were over capacity. Lancaster Prison had 70 too many inmates and HMP Preston 300 too many, its report found.
It criticised the number of inmates in a cell and time spent locked up.
Blackburn MP Mr Straw said Preston had "transformed" cell sanitation and the number of inmates sharing.
After a survey last month, HMP Preston was named on Tuesday as joint third in a list of 10 prisons with the highest level of overcrowding.
Mr Straw, who heads the government department responsible for the Prison Service, claimed the figures did not reflect the workable capacity a prison could hold.
"We have increased prison capacity, we have done it in Preston and Lancaster last year and are doing so in the next 12 months," Mr Straw told BBC Radio Lancashire.
In a bid to reduce prison populations, the report suggested more money should be spent on crime prevention, drug treatment and facilities for dealing with mental health problems.
Geoff Dobson, deputy director of the Penal Reform Trust, said that if these measures were introduced, prisons would be in a better position to deal with serious offenders.