Analysis published by the Howard League for Penal Reform on Friday suggests the increase is part of a national trend.

Eleven prisoners in the North West committed suicide in 2002 - out of 94 inmates taking their own life across Britain.

That compares to the figure of five prisoners in the previous year.

This level of suicides is not acceptable in a civilised society. Frances Crook, director of the Howard League

Liverpool, Preston and Cheshire's Styal prison, have the highest rates in the region.

But the figures show the suicide rate has remained unchanged at both Liverpool and Manchester prisons.

The Howard League said it believed the increase was primarily caused by overcrowding.

It called on the government to act to reduce the number of people in prison in order to save lives.

'Improvements undermined'

Frances Crook, director of the Howard League, said: "This level of suicides is not acceptable in a civilised society.

"The improvements to prison regimes being attempted by the prison service in the last couple of years have been undermined by the sheer number of people now being sent to prison by the courts.

"People have paid for the degrading and inhumane conditions in our overcrowded prisons, with their lives.

The Home Secretary must act now to end this tragic loss of life."