Police monitors sued the Met and Home Secretary Theresa May yesterday for keeping activists' details on a database of "domestic extremists."

Lawyers for non-profit police watchdog Netpol went to the High Court to challenge the Metropolitan Police's snooping effort.

The database contains a variety of personal details of about 9,000 people.

Many of those listed on the national domestic extremism database have never committed a crime.

Leigh Day solicitors want to start a judicial review against the Met and Ms May.

They said that the police's continued collection of personal data of people involved in protests breached their rights to a private life under article eight of the Human Rights Act.

"The database is not established under legislation and there exists no sufficiently clear, precise or accessible policy setting out its scope and purpose," said solicitor Rosa Curling.

"There also does not appear to be in place any effective mechanism to continuously review the database and identify material which should be deleted."

Political campaigner John Catt succeeded earlier this year in his bid to have his details removed from the database.

Mr Catt, an 88-year-old from Brighton with no criminal record, attended demonstrations against the local EDO arms factory, where he had his details recorded by the National Public Order Intelligence Unit.

Following a request under the Data Protection Act, the agency was found to hold details of his appearance, his vehicle, demonstrations he had attended and other personal details.

Mr Catt initially failed in his bid to have his details removed from the database, with the High Court finding that his right to privacy had not been infringed.

But the Court of Appeal overturned that ruling in March, saying that the information fell "within the scope of (Mr Catt's) personal autonomy over which he is entitled to retain control."

The judges said that in Mr Catt's case the retention of this information was disproportionate and unjustified.

They added that it appeared officers had been recording "the names of any persons they can identify, regardless of the particular nature of their participation."