Jonny Wilkinson is calling on England's rugby stars to eradicate the errors that have been punishing them in games ahead of their World Cup defence.Brian Ashton's men have suffered back-to-back defeats in successive weeks at the hands of hosts France and know they have much work to do if they are to have any chance of becoming the first nation to retain the Webb Ellis trophy.The world champions followed up their 21-15 reverse at the hands of the French at Twickenham with a 22-9 defeat in Marseille last Saturday.And 2003 World Cup hero Wilkinson reflected: "We need to hold on to the ball - that is where tries come."It is simple for us. We know it is all there, and we know what the answer is. We just need to let it all come through by knocking on the head these errors. It is about holding our discipline, creating pressure and gaining momentum."World Cup captain Phil Vickery will undoubtedly enforce similar messages, assuming he is fit for England's tournament opener against the USA on September 8.The Wasps prop was concussed in a midfield collision at Stade Velodrome, and while early signs did not look good as Vickery was stretchered away, the England camp remain positive about his recovery prospects.Ashton said: "Phil is fine. The (England) doctor said to me you just do not know in these situations until 24 or 48 hours down the line."He said 50 per cent of guys (concussed) in the Guinness Premiership play the following week, and the way Phil was yesterday morning, the indication is he will be fine come the start of the World Cup."© Independent Television News Limited 2007. All rights reserved.