The National Archives have released further documents detailing the historic surveillance of a prominent Jewish member of the Communist Party.

Sam Aaronovitch became secretary of the party's National Cultural Committee in the 1940s, later serving as Party Secretary in the Central London area.

Mr Aaronovitch's activities were closely monitored, firstly by local police forces, and subsequently by MI5.

His correspondence was opened regularly, and both phone- and wire-taps of the Communist Party headquarters picked up conversations in which he participated or was mentioned.

His son, journalist David Aaronovitch, published Party Animals, an account of growing up in the party, in January. He said the new documents revealed a "quite surprising" level of intrusion.