Before her ennoblement by Tony Blair, Cathy Ashton served as treasurer of the Campaign for Nuclear Disarmament from 1980 to 1982, the second most senior role in the unilateralist organisation.

She joined the movement in 1977 when she became a paid organiser, and represented CND at meetings in her native north-west to promote its call for Britain to give up its nuclear deterrent.

Lady Ashton is likely to have come to the attention of the security services, like several of her activist comrades, although allegations that she was kept under surveillance have not been confirmed.

In 1980, records show that she was part of a CND delegation that went to the Netherlands to meet a communist-controlled group called Stop The Neutron Bomb, which campaigned against American nuclear weapons.

Documents obtained by UKIP show that the first audited accounts of CND, for 1982-83, found that 38 per cent of its annual income, or £176,197, could not be traced back to the original donors.

Gerard Batten, a UKIP MEP, has written to the European Commission asking if it believes Lady Ashton should be entrusted with EU security policy.

He wrote: “The Russian dissident and internationally respected figure Vladimir Bukovsky has proven with hundreds of top secret documents from Soviet archives that the worldwide disarmament campaign in the 1980s was covertly orchestrated from Moscow. Money was channelled through communist parties or other pro-Soviet organisations and individuals. It therefore seems very likely that unidentified income came from the Soviet bloc.”

Lady Ashton addressed such claims in her report to CND’s annual conference in 1982, where she argued for audited accounts. “CND has suffered many smears this year, which have pointed to where our funding comes from,” she said.

“It should be pointed out that an audit will not provide the ultimate answer to the smear as it cannot tell whether an individual is giving money from sources that we would not wish to have finances from.”

Dan Smith, a predecessor to Lady Ashton as treasurer of CND, defended her reputation yesterday.

“We were on the national council and executive at the same time and I think it is nonsensical to say that money came from the Soviet Union,” Mr Smith said.

“The reason why sources of money could not be traced was because a lot of it was cash collected in buckets at meetings in towns and villages. The money came from ordinary people.

“It is not like someone put in £25,000 and there was anonymity. What was said by auditors was that some of this money comes from sources which of their nature cannot be traced. In the early 80s, people just put a £5 postal order in an envelope and sent it.”

Mr Smith added that he was accused by the Federation of Conservative Students of being a Soviet agent and won a libel case against them. “I see this being raised again now as outdated student politics.”

He recalled that Lady Ashton was not among those CND members who campaigned for Britain to withdraw from Nato. “We did not like the Nato strategy on the possible first use of nuclear weapons. We did not like the Soviet Union for this either. We saw Nato as a western alliance and we wanted its strategy to change. There was a call from people who were supporters of the CND to withdraw from Nato but CND was a broad church, you had absolute pacifists and others, and it was not CND policy to withdraw from Nato.”

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