The publisher said Rendell, 84, whose best-known creation Chief Inspector Wexford became a popular television series, suffered a "serious stroke" on January 7.
Other works including many of her short stories were also successfully adapted for television as "The Ruth Rendell Mysteries".
Translated into 25 languages, her work delved into the darker recesses of the criminal mind.
Jean-Claude Berline, the French editor of her next book, said that Rendell "has been in a coma for several days and it seems that it is irreversible".
Scottish crime writer Ian Rankin called the development "grim news".
"Comes so soon after we lost P.D. James," he wrote on Twitter. "Wishing her a full and speedy recovery."
Rendell's fictional creation, the sensitive Chief Inspector Reginald Wexford, featured in her first novel "From Doon to Death" (1964) and throughout her career.
The elderly detective only retired in "The Vault" (2011) but she continued writing and her latest book, "The Girl Next Door", came out in 2014.
Appointed Baroness Rendell of Babergh by Queen Elizabeth II in 1997, she became a member of the House of Lords, the UK parliament's upper house.
Responding to the news, Labour Lords UK, the grouping's official Twitter account, said: "Our thoughts are with our colleague Ruth Rendell and her family following her serious stroke & we hope to see her back in the Lords soon."
The writer has been awarded four Gold Daggers and a Diamond Dagger from England's prestigious Crime Writers' Association, as well as three Edgar Awards from the Mystery Writers of America among many other accolades.
She was a close friend of fellow British crime writer P.D. James, who died in 2014 at the age of 94.
Berline said that after P.D. James's death, Rendell was "the last grande dame of the police thriller".
Rendell was born Ruth Grasemann in 1930 into a family of teachers. Her mother was born in Sweden and brought up in Denmark and her father was English.
She started out as a journalist, writing feature copy for a local paper, the Chigwell Times, but was forced to resign after reportedly inventing stories.
She married Don Rendell in 1953 and two had a son. Her husband died in 1999 from prostate cancer.
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Other works including many of her short stories were also successfully adapted for television as "The Ruth Rendell Mysteries".
Translated into 25 languages, her work delved into the darker recesses of the criminal mind.
Jean-Claude Berline, the French editor of her next book, said that Rendell "has been in a coma for several days and it seems that it is irreversible".
Scottish crime writer Ian Rankin called the development "grim news".
"Comes so soon after we lost P.D. James," he wrote on Twitter. "Wishing her a full and speedy recovery."
Rendell's fictional creation, the sensitive Chief Inspector Reginald Wexford, featured in her first novel "From Doon to Death" (1964) and throughout her career.
The elderly detective only retired in "The Vault" (2011) but she continued writing and her latest book, "The Girl Next Door", came out in 2014.
Appointed Baroness Rendell of Babergh by Queen Elizabeth II in 1997, she became a member of the House of Lords, the UK parliament's upper house.
Responding to the news, Labour Lords UK, the grouping's official Twitter account, said: "Our thoughts are with our colleague Ruth Rendell and her family following her serious stroke & we hope to see her back in the Lords soon."
The writer has been awarded four Gold Daggers and a Diamond Dagger from England's prestigious Crime Writers' Association, as well as three Edgar Awards from the Mystery Writers of America among many other accolades.
She was a close friend of fellow British crime writer P.D. James, who died in 2014 at the age of 94.
Berline said that after P.D. James's death, Rendell was "the last grande dame of the police thriller".
Rendell was born Ruth Grasemann in 1930 into a family of teachers. Her mother was born in Sweden and brought up in Denmark and her father was English.
She started out as a journalist, writing feature copy for a local paper, the Chigwell Times, but was forced to resign after reportedly inventing stories.
She married Don Rendell in 1953 and two had a son. Her husband died in 1999 from prostate cancer.
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