Mrs Campbell first began her campaign for improved jail conditions after the death of her 18-year-old daughter Sarah in Styal prison in 2003.

She then protested tirelessly up and down the country following subsequent deaths at women's prisons – including those of Fylde women Helen Cole and Lisa Marley.

Mrs Campbell, from Whitchurch, Shropshire, was found dead at Oakhills cemetery in Malpas, Cheshire, by a member of the public at 6.15am yesterday.

Today prison reform groups paid tribute to the "single most effective and inspiring campaigner for penal reform in recent years".

Mrs Campbell, wanted improved observation of inmates and better custodial care.

Prison Reform Trust director Juliet Lyon said: "Pauline Campbell campaigned bravely and tirelessly to save other families from having to endure the unbearable pain of losing a child through suicide in prison.

"Her death makes me so sad."

Mrs Campbell's protests led her to being arrested 15 times.

More recently, the 60-year-old was accused of obstructing a road when she led a protest rally at HMP Styal following the death of Miss Marley.

The 32-year-old mother, of Lostock Gardens, South Shore, was found hanged in her cell in January this year while on remand.

After the Crown Prosecution Service dropped the charges, Mrs Campbell, last week told The Gazette: "From start to finish, this senseless prosecution was a waste of the court's time, a scandalous waste of public money and an enormous drain on my emotional health.

"I believe in standing up for principle because it is one of the few ways in which people can make a difference.

"I refuse to bow to pressure and will stick to my resolve to hold prison death demonstrations outside jails in England when women kill themselves in the so-called care of the state.''

Loving

Mrs Campbell also protested outside Styal prison after Helen Cole, 48, of Belvedere Road, Thornton, was found hanged in her cell while held on suspicion of murdering her teenage son Andrew in May 2007.

Frances Crook, director of the Howard League for Penal Reform, where Mrs Campbell was a trustee, said: "Pauline Campbell was a loving mother, a generous-hearted woman and a human being of indescribable bravery.

"Pauline was also the single most effective and inspiring campaigner for penal reform in recent years.

Her uniquely courageous voice will live on, as it must, for as long as injustice remains in our society.''

Cheshire Police said there were no suspicious circumstances surrounding Mrs Campbell's death.