Footballers were today warned that spitting could increase the risk of spreading swine flu as players at two Barclays Premier League clubs were struck down by the virus.

The Health Protection Agency (HPA) said the "disgusting" habit - a common sight at many matches - could lead to infections being passed on.

Blackburn and Bolton both have a number of players showing signs of the virus ahead of their Carling Cup matches this week.

The HPA said spitting should be discouraged by football clubs as experts attempt to halt the spread of the infection.

"Spitting is disgusting at all times. It's unhygienic and unhealthy, particularly if you spit close to other people," said an HPA spokesman.

"Footballers, like the rest of us, wouldn't spit indoors so they shouldn't do it on the football pitch.

"If they are spitting near other people it could certainly increase the risk of passing on infections.

"Certainly, spitting is a nasty habit that should be discouraged - and it should be discouraged by the clubs.

"It's about setting examples for young people who idolise them."

He added footballers should follow the same guidelines as other members of the public by washing their hands, covering their mouth when sneezing and disposing of used tissues.

"The advice is catch it, bin it, kill it," he said.

The Football Association and Barclays Premier League said they were following guidance from health experts in handling the issue.

"As ever, when it comes to health matters the Premier League will be guided by the relevant statutory authorities," said a Premier League spokesman.