A database compiled by researchers at the University of Cambridge said 21 spoken traditions are at risk of becoming extinct in the United Kingdom, including Old Kentish Sign Language.

Of the 3,524 languages named in the database, around 150 are in an extremely critical condition with some retaining only a handful of known speakers.

Dr Mark Turin, director of the World Oral Literature Project which is based at the university, said: "At present, the database allows us to pose comparative research questions about which languages are closest to extinction and where the records are."

He added: "While some severely endangered languages have been well documented, others, which may appear to be less at risk, have few, if any, records."

Researchers hope the site will enable them to gather further information and to uncover associated folklore, stories and myths.

Another endangered UK tradition on the list is Polari, a code language used by the gay community up until the 1970s. Records show it now has only a handful of remaining speakers.

Its origins are disputed but it is thought it could date as far back as the 16th century when it was spoken by market traders and circus workers.

More recently, Morrissey named his 1990 compilation album in the Polari 'Bona Drag', meaning "nice outfit".

The database has been launched to coincide with a workshop at the Centre for Research in the Arts, Social Sciences and Humanities (CRASSH) at the University of Cambridge.