Blow to Boris as Ross quits Olympic role

Ex-Carphone boss is Mayor's fourth appointee to resign in eight months

David Ross, the businessman who resigned over a £130m shares scandal on Monday, yesterday quit his role as a key Olympics adviser to the London Mayor, Boris Johnson. He also stepped down as a director and chairman of the transport group National Express.

In another blow to the Tory Mayor's credibility, Mr Ross became the fourth of Mr Johnson's personal appointees to leave their post in eight months. He resigned his seat on the board of Carphone Warehouse, the telecoms company he co-founded, on Monday after he admitted using his shareholding as collateral for personal loans – in a potential breach of City rules.

Mr Johnson appointed Mr Ross, 43, as his representative on the London Organising Committee of the Olympic Games and chairman of the Legacy Board of Advisers, which aims to ensure a lasting economic and cultural legacy from the 2012 Games. Mr Ross also sat on the board of the Olympic Lottery Distributor, which co-ordinates lottery funding for the event.

Yesterday, however, Mr Ross, an ally of the Tory leader David Cameron, tendered his resignation to Mr Johnson and the Olympics minister Tessa Jowell. "I reach this decision with sadness as I have very much enjoyed making this contribution to British sport, which has been a lifelong passion," he wrote. "However, given the present circumstances, and while they are not connected to the Olympics, I must now devote my full attention to my private business interests. I also do not wish to distract others from the important work still to do in making 2012 the success I know it will be."

Mr Johnson, who had stood by Mr Ross, said the tycoon played an "active and very useful role", adding: "I am particularly grateful to him for identifying serious issues with the 2012 Games that needed to be urgently addressed. His report into planning the delivery of legacy of the Games helped the entire Olympic family to focus on a range of pressing concerns, including security, budget and legacy."

Mr Ross founded Carphone Warehouse with his schoolfriend Charles Dunstone, and built up a fortune estimated at £873m. He is a prominent Tory donor and was considered as the party's London mayoral candidate to stand against Ken Livingstone before Mr Johnson emerged as the favourite.

Mr Ross is the latest senior mayoral aide to step down since Mr Johnson's election in May. The others were the Mayor's chief political adviser, James McGrath, the deputy mayor for young people, Ray Lewis, and Tim Parker, the chairman of Transport for London.

Mr Johnson's opponents argued that, while one departure could be seen as bad luck and two a slight concern, four raised questions about the Mayor's vetting procedures. John Biggs, the deputy Labour leader on the London Assembly, said: "There is no doubt this was a serious mistake by Mr Ross, but the greater error was from the Mayor, appointing him to such an important position within his administration."