Rimington and Filkin were advisers to ad firm facing High Court closure

The former head of MI5, Dame Stella Rimington, and Elizabeth Filkin, the former Commons standards watchdog, were both advisers for several months last year to the company Standards for Promotions Inspectorate Ltd (SPI), which faces being wound up by the High Court next month after "grave reservations" were raised about its operations.

Company inspectors based at the Department of Trade and Industry are to ask the High Court to wind up SPI – now in the hands of the Official Receiver – in the public interest.

Styling itself an independent advertising standards body, SPI contacted the chief executives of some of Britain's largest firms, including British Airways, Cadbury and Nestlé, offering its services for six-figure sums.

Using the name SPi Inspectorate, it took out ads in Whitehall and industry journals claiming it had the endorsement of the consumer affairs minister, Melanie Johnson, and leading lawyers and European Commission officials – claims that have been strenuously denied by those involved.

Its sales pitch included plans to organise a major industry "summit" – allegedly sponsored by organisations such as the European Commission and Vodafone. It was touted as a, "unique conference [which] will demonstrate how the scams and rogue traders can be identified". The event did not take place, and SPI is alleged to have outstanding debts running into hundreds of thousands of pounds.

Ms Filkin admitted to The Independent on Sunday that last autumn she had helped lobby Whitehall civil servants on behalf of SPI, which was set up by a London-based businessman called Salvadeor Priost in February last year.

Ms Filkin said she was approached to help the firm by Dame Stella last August but said she now regretted being involved and found her experience "very upsetting".

Ms Filkin said she was attracted by the firm's claims that it would give expert help to Britain's leading businesses on making sure their advertising campaigns were legal, would set up a "definitive code of practice" on advertising promotions and crack down on rogue competition promoters.

Ms Filkin said she agreed to become a non-executive director of the company and initally helped the firm by lobbying civil servants at the Office of Fair Trading to meet with SPI executives and to introduce them to the Department of Trade and Industry.

But Ms Filkin claimed that, despite her name being registered at Company's House, her directorship was a "mistake" and did not formally come into force because the firm's rules limited the size of the board.

Ms Filkin insisted she had severed all her links with the firm after becoming increasingly doubtful about its operations several months after being first being approached, and her name was removed from the list of directors in December last year.

Dame Stella, now a director of Marks and Spencer, confirmed she had also been a director of the firm until early December, but "had had no connection with the company since that time". She refused to answer any further questions.

Edward Mutton, director general of the Institute for Sales Promotion – the main industry trade association – said his organisation had "grave reservations" about SPI's operations. The industry already had "robust" codes of conduct and legal standards, overseen by the Advertising Standards Authority and his association, he said, and did not need any other self-regulatory bodies.

Mr Priost could not be traced last night, and no telephone number was available for his firm's business address in central London.