Speaking through his lawyers, Mishcon de Reya, the best-selling author and Tory peer said he now had the 'deepest regret' over the 'embarrassment needlessly caused to Lady Archer'.
Although admitting he made a mistake in placing an order for 50,000 shares in Anglia Television four days before a pounds 292m takeover bid by MAI sent the share price rocketing, Lord Archer, the former deputy chairman of the Conservative Party, continued to maintain that the 'transaction was not carried out with the benefit of any insider information'.
The statement added he had made a 'grave error' because he 'allowed his name to be associated with the purchase and sale of shares in that company on behalf of a third party (and from which he in no way benefited)'.
The shares were registered in the name of an Iraqi associate of Lord Archer, Broosk Saib, but the cheque for the profit from the sale was sent to Lord Archer's address. Mr Saib, although admitting this week that he had a 'private deal' with Lord Archer, would not confirm who the beneficiary of pounds 80,000 profit was.
Labour last night seized on Lord Archer's admission. Robin Cook, shadow Trade and Industry Secretary, said he had 'confirmed that all the allegations of the past week are true and were in the DTI report. It is now even harder to understand why Michael Heseltine decided to take no action if he knew of all the allegations and knew they were true.'
Mr Cook added: 'Today's admission by Lord Archer makes it all the more important that we get a second opinion on the DTI report. We need to know that the decision to take no further action was made on legal rather than on political grounds. We must never again let a senior Tory politician sit in judgement on another Tory politician.'
As Tory Central Office declined to comment on the detail of the statement, Mr Cook said the issue should be referred to a body such as the Crown Prosecution Service to decide whether an offence had been committed and whether a conviction could be secured.
The statement casts further doubt over Lord Archer's hopes of regaining political office as a reward for his campaigning on behalf of the Conservative Party. His office had earlier dismissed a report that he was intending to back out of politics altogether. Tory Central Office insisted they would be happy to see Lord Archer, as a 'very popular figure', continue in his campaigning role.