Barbara Castle was targeted in honey trap by a communist spy who she described as a “gentle Italian flower”, the Telegraph can reveal.

The Labour firebrand was wined and dined by Renato Proni, who under the codename Andrej had pledged allegiance to the Czechoslovakian secret police and who boasted to bosses in Prague that he thought he could seduce her.

It is not believed that Baroness Castle succumbed to his advances, but the pair became “very close” and the relationship was frowned upon by others, intelligence documents unearthed by this newspaper reveal.

The married MP, who went on to hold a succession of Cabinet posts under Harold Wilson and was targeted because of her connections, is the latest in a series of senior Labour figures revealed to have had contact with spies from the Soviet bloc.

Among them are Jeremy Corbyn, the current party leader, who met an agent of the Statni Bezpecnost (StB), the Czechoslovakian secret police, in the late 1980s and Geoffrey Robinson, the Paymaster General under Tony Blair, who met an agent in the late 1960s.