CARDIFF, United Kingdom: England have found themselves at the centre of a tampering row after former captain Bob Willis accused them of scratching the ball.       The alleged incident took place during England's seven-wicket Champions Trophy one-day international defeat by Sri Lanka at The Oval on Thursday when Pakistani umpire Aleem Dar and his his New Zealand on-field colleague Billy Bowden ordered one of the balls in use to be changed while the Lankans were batting.       "Let's not beat about the bush -- Aleem Dar is on England's case," Willis told Saturday's edition of the Sun tabloid.       "He knows that one individual is scratching the ball for England -- who I am not going to name -- and that's why the ball was changed," insisted Willis, one of England's greatest fast bowlers.       "Have you ever heard about the batting side or the umpire complaining about the shape of the ball?" added Willis, on of only four England bowlers to have taken 300 Test wickets.       Under current rules for one-day internationals, two white balls are in use for each innings.       Balls can be changed for legitimate reasons, such as being knocked out of shape as a result of forceful hits by batsmen, and are often done so at the request of the fielding side.       However, on Thursday it appeared that it was Sri Lanka's Kumar Sangakkara who complained about the condition of the ball when his side were 119 for two at the halfway stage of their reply to England's seemingly imposing 293 for seven.       England were unhappy as their attack was starting to gain reverse swing, which was key to their opening victory over Australia and is aided by natural wear and tear of the ball, with captain Alastair Cook leading the protests.       However, the replacement ball moved little and Sangakkara went on to complete a superb unbeaten hundred to guide Sri Lanka to victory.       After the match, Cook said: "The ball was changed because it was out of shape. The umpires make these decisions and you have to accept them. Sometimes you don't think they are the right decisions."       But Willis, an England captain in the early 1980s, told the Sun: "How naive does Alastair Cook think we are? He didn't want the ball changed. So why was it changed?       "It is OK for the ball to scuff through natural wear and tear -- but against cricket's laws to use fingernails or other means to alter its condition."       Australian umpire Darrell Hair, together with West Indies' Billy Doctrove, docked Pakistan five runs for ball-tampering during a controversial Test against England in 2006.       Pakistan subsequently forfeited the match in protest -- the first time this had happened in Test history.       They were subsequently exonerated by an International Cricket Council (ICC) investigation and the ensuing row ultimately cost Hair his career as a senior international umpire.       However, the match officials in the England-Sri Lanka match took no similar action and the ICC explained that as the umpires haven't reported anything and no team has complained, they were not planning to take any action.       England must beat New Zealand in Cardiff on Sunday to seal a semi-final spot. If they lose they are out and either Australia or Sri Lanka will go through after their match on Monday.       If the England-New Zealand match is a washout they will need a low scoring Australia victory to go through. If both matches are washed out, England will qualify behind New Zealand.