The Thresher chain was responding to reports that the Home Office had discovered that John Onanugu, 31, had overstayed a holiday visa two and a half years ago, and had since been living in Britain illegally.
A spokeswoman for Thresher said the company had checked the job application form Mr Onanugu had filled out two years ago, along with job references, and concluded that he 'had been perfectly entitled to work for us'.
'As far as we are concerned today, the information that he gave us has not altered, and he is therefore still employed by us.'
She said Mr Onanugu, a Nigerian, possessed a national insurance number and had worked for another well-known company before joining Thresher.
The new development in the affair came at the weekend with press reports that the Home Office had discovered the irregularities during routine inquiries shortly before Christmas. One report quoted sources which said Mr Onanugu was likely to be served with deportation papers in the next few days.
The Home Office confirmed yesterday that Charles Wardle, the minister responsible for immigration matters, had been informed. A spokeswoman said: 'Mr Wardle is aware of the case. He will either make a decision himself, or at least be aware of any decision by his officials.'
Mr Wardle's direct involvement in the case is politically necessary because of the part played by Mr Onanugu in the embarrassment caused to Norman Lamont, the Chancellor of the Exchequer, last November. Mr Onanugu falsely claimed that Mr Lamont had used his Access card to buy pounds 17.47 of champagne and cigarettes from the Thresher store in Praed Street, West London.
However, the company later said that Mr Onanugu, along with his manager David Newton, had lied, and confirmed that Mr Lamont had bought some wine from another Thresher shop.
After a disciplinary inquiry, Mr Newton was sacked, while Mr Onanugu, who had posed for press photographs with a bottle of champagne, had been disciplined, but allowed to keep his job.
Mr Onanugu was not at home at his flat in Herne Hill, south London, yesterday. He lives there with his girlfriend Bernadette, and their seven-month-old son Abdul.