A senior supporter of Sir Ken Jackson, a favourite union leader of the Prime Minister, allegedly wiped computer records in an "amateurish'' attempt to cover up vote-rigging.
The top official at Sir Ken's union, Amicus-AEEU, has been accused of complicity in the scam, which was aimed at concealing the involvement of the organisation's headquarters in the ballot-rigging.
Roger Maskell, regional secretary for the union in south-east England, has been asked to appear before senior officials investigating malpractice at meetings to nominate Sir Ken as general secretary.
The Prime Minister, who is anxious that Sir Ken remains leader of the union after his normal retirement date, will be deeply concerned about the fresh revelations.
Original print-outs showed that officials at the union, which gave £2m to Labour's election campaign, had been moved from branch to branch, nominating Sir Ken at each. The records were changed, but after the union's returning officer had seen the originals.
The fresh accusations – there is no suggestion that Sir Ken is involved in malpractice – come after the union's executive set up a three-man inquiry team to look into vote-rigging ahead of the election which will take place between 24 June and 12 July.
Three officials – Geoff Saunders, Rob Johnston and Stuart Wallis – had admitted they each voted twice to nominate Sir Ken. A fourth, Kevin O'Gallagher, was also found to have been among the "flying voters.'' It is understood that other documents allege that another man voted three times.
A letter to Sir Ken from Derek Simpson, a left-winger from Derby challenging for the top post, alleges that top officials must have been involved in the cover-up. "This could only have been possible with the complicity of senior staff. My concern is that there is complicity at the highest level, first in an amateurish attempt to cover up the malpractice of full-time officer branch- transfers and then a more sophisticated attempt to cover up the cover-up in advance of a detailed investigation by the executive council.''
However, a spokesman for the union yesterday said Sir Ken had openly ordered the second alteration so that the data was accurate.
A union spokesman said Mr Maskell had made no official response to the allegations. Last night Mr Maskell was unavailable for comment.
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