• Midfielder defies Arsenal rules by cutting long-sleeve shirt • 'I do not like that and he will not do that again,' insists Wenger

Arsène Wenger gave one of his players a public dressing-down in a bizarre ending to a night that saw Jack Wilshere's two goals put Arsenal on the brink of qualifying for the knockout stages of the Champions League.

Arsenal, with four wins from their five group games, will go through if they avoid losing by three goals or more against Napoli at Stadio San Paolo on 11 December, but Wenger was unhappy with Mathieu Flamini.

The French midfielder has developed a habit of taking a pair of scissors to his shirt to turn it into a short-sleeved top. Flamini had been involved in a row with the kitman, Vic Akers, before and after his last game, when he did the same against Manchester United, and this time Wenger made it clear he considers it a breach of club rules. "I do not like that and he will not do that again," he said. "I was surprised he did that; we don't want that."

Arsenal's rule is that the players must all wear the same shirt and that it is selected before every game by the captain. However, an odd finale to an otherwise satisfactory night took another twist when Flamini indicated he would continue defying his manager. "I've been playing at the top level for 10 years," he said. "I like to wear short sleeves, that's what I like to do."

Olivier Giroud also had short sleeves, though in his case he had rolled them up rather than snipped them off, on a night when Wilshere scored as many goals as he has previously managed in an entire season.

The first came after only 33 seconds, from a player who had scored only seven times in his previous 115 Arsenal games. "I've never scored four goals in a season before. I've set myself a target of 10 and hopefully I can reach that."