Crozier condemned as "unacceptable" the scenes during Cardiff's 2-1 FA Cup third round win over Leeds, with players and officials pelted with missiles.

Police also had to restrain fans who had invaded the Ninian Park pitch.

And during Wednesday's Worthington Cup semi-final between Chelsea and Spurs, projectiles were thrown at several players.

A beer bottle narrowly missed hitting Spurs striker Les Ferdinand after he equalised in the 65th minute at Stamford Bridge.

"Clearly, the events off the field at Cardiff are unacceptable for a multitude of reasons and can't be tolerated," Crozier told the Daily Telegraph.

"We are full-steaming into the investigation. We made sure we got involved in the FA of Wales' investigation.

"There are pockets of trouble in football but we should not forget that all of the clubs have done a fantastic job - in conjunction with stewards and police - at ensuring that going to football in England is great fun.

"What happened at Cardiff reminds us that we can never rest on our laurels.

"We must never take our foot off the gas because hooliganism has to be controlled."

The FA chief also believes that pitch invaders, such as those Manchester United fans who spoiled a fantastic FA Cup tie at Villa Park, should be punished with more than the standard �100 fine.

He added: "Ourselves, the Football League and Premier League are constantly lobbying the Government to make sure that if someone does something wrong at a football match, they are properly punished.

"What happened at Cardiff was a shame because it was a terrific FA Cup weekend with great drama spoiled by some events off the pitch.

"The Cup has got off to a fantastic start and we have a very exciting league season, so everyone needs to concentrate on being successful on the field and concentrate on their own performance.

"Around the turn of the year, when games are coming thick and fast and seasons are made or broken, adrenalin always runs very high.

"People have got to just calm down."