One of the co-founders of UK retailer the Carphone Warehouse has tendered a surprise resignation over the improper use of his shares.

David Ross, who owns 19.4 per cent of the company he founded with school friend Charles Dunstone, used 136 million of his 177 million shares as security against personal loans without telling anyone in the company.

The stock exchange requires that a public announcement is made if shares are used in this way, and while it appears Ross has complied with the rules in the past, he has failed to notify the company about more recent loans secured in this way.

Carphone said that Ross has notified the company that none of these loans is currently in default and that he has no current intention to sell any of his shares in the company.

“David Ross has tendered his resignation as a Director of the Company with immediate effect and will continue to pursue his various other business interests,” Carphone said.

The retailer said no other director of the company has granted security over or entered into any financial instruments relating to any of their holdings of ordinary shares in the firm.