Wasps have denied that a training-ground incident between Danny Cipriani and Josh Lewsey yesterday was anything more serious than a disagreement between team-mates, the kind frequently seen on the rugby pitch. But reports today suggest the club are launching an investigation into claims that the full-back Lewsey punched Cipriani, cutting his nose and lip, and leaving him requiring smelling salts to come around.

"Rugby is a fiery and physical game, and incidents like this happen in training sessions all the time," said a Wasps spokesperson. "There is no issue and there is no problem between Danny and Josh. They are friends and team-mates."

However after the story broke in several morning papers, prompting the club's statement, the London Evening Standard this afternoon quoted a Wasps insider, who said that Cipriani was knocked out by his team-mate. "It was certainly one hell of a punch because Danny was out cold."

The England pair clashed after Lewsey criticised Cipriani for missing tackles during a one-on-one contact training drill, prompting the No10 to respond with "Shut up or be shut up". But it was the younger player who was apparently silenced by Lewsey's fist.

The defending Premiership champions have lost five of their first six games but turn their attention this weekend to the Heineken Cup and a home tie against French club Castres, where Cipriani is set to make his second appearance after returning from a serious ankle injury. Earlier this week, the England fly-half explained how the Wasps' coach, Shaun Edwards, had told his players to step up their intensity for the visit of Castres.

"We will be more aggressive, we will run harder and we will have that edge that we lacked," Cipriani said. "It is about time we stand up and make our fans proud. Shaun Edwards has hit home with a few truths and really made a few points clear to some of the guys. We needed it and it needed to be said."