BERLIN - Verena Becker, the former German Red Army Faction (RAF) member arrested last week over her links to a spectacular political murder committed 32 years ago, worked for years as a secret service informant, it emerged yesterday.

Becker, 57, was paid to help capture leaders of the left-wing terrorist group, also known as the Baader-Meinhof gang, according to senior former intelligence figures who spoke in a television documentary screened in Germany yesterday. The revelations came after she was arrested at her home in Berlin last Saturday when police found new evidence implicating her in the killing of Siegfried Buback.

The chief West German federal prosecutor was shot dead in 1977 by masked RAF faction attackers on a motorcycle while he was driving to work in Karlsruhe.

The arrest seemed to provide an answer to a mystery surrounding one of post-war Germany's most notorious murders, particularly implanted in the public consciousness since its brutal depiction in last year's film, The Baader-Meinhof Complex.

But yesterday's revelations have further complicated the story. While Becker was caught and jailed for life in 1977, it was not for the Buback killing. She was sentenced instead for seriously injuring a policeman whom she shot shortly before her arrest.

Freed on compassionate grounds in 1989, until last week she had been living under a new name in Berlin.

Michael Buback, the murdered man's son, said yesterday that he was convinced that the authorities had protected Becker.

"For my wife, Elizabeth, and myself it has become a certainty that the perpetrators on the motorcycle were not punished for their crimes, and that there was a protective hand shielding one RAF woman terrorist," he said in an interview with Germany's Die Zeit magazine.

In yesterday's film on the ARD channel, former intelligence officials said that Becker was a paid informant for German security services on the RAF. "Becker turned to us because she found herself in a difficult personal situation," said Winfried Ridder, a former intelligence officer.

He disclosed how Becker provided the crucial tip-offs that led to the arrest of RAF leaders Brigitte Mohnhaupt and Christian Klar, who were only recently released from prison after serving life terms for the Buback killing and other murders carried out by the gang.

Becker also provided key information on the RAF's structure and decision-making processes.