Prison service figures show that by the end of 1998, there were 4,011 "lifers" in jails in England and Wales - a 40% rise on the average of the previous decade.
Most are serving mandatory life sentences for murder and the trust is calling for this to be abolished in favour of giving judges discretionary power as is the case elsewhere in Europe.
The trust says that the UK is following the experence of the US, with growing numbers of 'pensioner' prisoners.
Each year, between 80 and 90 inmates are released from life sentences, but 300 enter the system.
Budget cuts
This upward trend is likely to be exacerbated by the 1997 introduction of life sentences for people convicted of a second serious violent or sexual offence - although these sentences are discretionary and not mandatory.
Further pressure is placed upon the system by the fact that the average lifer in England and Wales stays in jail for 14.3 years, compared to 11.2 years in 1987.
The trust's report warns that although prisoners are spending longer in jail, previously successful schemes preparing them for release have suffered from budget cuts and staff shortages.
Prison Reform Trust director Stephen Shaw said: "The number of people serving life has now reached an unprecedented high.
"It is time we followed the example of other European countries and abolished the mandatory life sentence for murder, reserving it as the maximum sentence available to the court."
Northern Ireland
Scotland
Wales
England
Straw aims to cut re-offending
(11 Nov 98 | UK)
MPs demand cut in prison sentences
(10 Sep 98 | UK Politics)
Police watchdog attacks care of prisoners
(11 May 98 | UK)
Explosion in prison population predicted
(29 Jan 98 | UK)
The Prison Service
Home Office
British Society of Criminology
Prisons Handbook
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