Britain's biggest retailer Tesco has appointed Marks & Spencer's Chief Financial Officer Alan Stewart as its new Finance Director.The FTSE 100 grocer has been looking for a new Finance Chief since Laurie Mcllwee announced his plans to retire in April.Stewart's surprise resignation from M&S, where he had only recently been given extra responsibility for property as part of the company's boardroom reshuffle, was announced simultaneously on Thursday, in a move that City commentators branded was "out of the frying pan into the fire" with both companies under pressure from shareholders unhappy with their performance.A start date at Tesco has not been stated for Stewart, whose CV includes Chief Financial Officer roles at WH Smith and Thomas Cook, where he was promoted to UK CEO in 2001.Chief Exeutive Officer Philip Clarke said: "When we set out on this search we wanted a candidate who had the right blend of experience, leadership and values to play a leading role in the transformation of Tesco. We have found all three in Alan."As of 12:06 the share price risen by 0.08% to 279.7p.WS