By Mike Fox BBC correspondent in Montreal

The Canadian Hockey Association has launched a new campaign to persuade parents to put less pressure on their children while they are at the ice rink.

There is growing concern in North America about parents who place too much emphasis on performing well at ice hockey and the growing violence both on and off the ice.

We have some grown men and women yelling and scratching referees - some of those refs are only 12

Scot Keith, campaign organiser

Earlier this year, a father in the US state of Massachusetts was jailed for manslaughter for six years after beating another father to death in an argument about the game getting too violent.

It can be shocking to hear a mother shout at a child to stand up for herself, but the Canadian Hockey Association is also sending out the message that it is wrong for parents to use that sort of language towards their children.

'Relax - it's just a game'

Organisers of junior leagues across Canada are reporting more and more cases of parents demanding their children be tough, and even of fighting among mothers and fathers supposedly there to offer support and encouragement.

It seems to be the result of a few children being pushed too hard at hockey, partly in an effort to break into the highly lucrative professional game.

Parents are said to be putting too much pressure on their children

Scot Keith of the advertising agency behind the "Relax, it's just a game" campaign said there was a need to tackle problems.

"We got some parents getting into fights in the arena - we have some grown men and women yelling and scratching referees," he said.

"Some of these refs are only 12 years old.

"We have some people suing minor hockey and we have some parents who are just putting way too much pressure on their kids to perform."

The campaign tells parents to relax, reminding them that hockey is just a game.

It is also a game that has long been associated with violence among players, although this year a rule change in the professional league has cut back the numbers of fights and penalties.

Organisers are hoping both these moves will make the game more attractive for parents and their children.