DAVID ROSS, deputy chairman and co-founder of Carphone Warehouse, has resigned from the British mobile phone retailer's board after failing to declare that he had used most of his shareholding as security for personal loans.

Mr Ross also failed to declare similar arrangements at three other companies - National Express, the transport group where he is chairman; Big Yellow Group, the storage company where he is non-executive director; and Cosalt, the industrial services and leisure products group, where he is chairman. He has not resigned from those posts.

The failure to disclose the loan arrangements could prove embarrassing for Boris Johnson, the London mayor, who has appointed Mr Ross as his representative to the organising committee for the 2012 Olympic Games.

The Financial Services Authority, the market regulator, said directors required clearance from the chairman or chief executive for dealing in shares, which is broadly defined to include using them as security in loans.

Carphone said yesterday Mr Ross had disclosed belatedly on Sunday that he had used 136.4 million of his shares - or 15 per cent of the company's equity - as collateral on loans. Shares in Carphone lost almost three-quarters of their value in the past year. News that there is a risk that Mr Ross's holding will have to be sold left the shares down 3.5 per cent yesterday. (- Financial Timesservice)