Prosecutions have been launched against 10 licensees in the crackdown on showing live football games illegally.
The Federation Against Copyright Theft (FACT), backed by the Premier League and Sky, has warned that its officers are working their way through a hit-list of 1,000 pubs which it believes are regularly showing live games on Saturday afternoons.
It is illegal to show live football matches during the closed period between 2.45pm and 5.15pm on a Saturday as the FA Premier League attempts to keep up attendances at the grounds.
But many pubs have been losing business to houses that show football during the restricted time using foreign decoders.
FACT director-general Brian Conlon said: "Of the 400 pubs we've visited so far we've established that around 200 are showing the illegal games."
Ten new prosecutions had been brought, with paperwork on another 30 potential cases being considered. He added: "We want to stress that we don't want to prosecute pubs. We'd much rather they stopped broadcasting the games." He said it was "quite unlikely" that any pub issued with a first warning would be prosecuted, but a second offence would trigger legal action.
Alison McKay, licensee of the Grey Mare in Bolton, Lancashire, said: "They should be targeting the companies selling the decoders rather than pubs; we're just trying to make a living.
"What's not fair is that some of us are obeying the law and losing trade, while others are making a killing. We all need to know exactly where we stand."
Some pubs claim to have been misled by firms selling the decoders which enable UK pubs to screen foreign Premiership coverage.
Ian Bodley, licensee of the Victoria pub in Witham, Essex, which shows the games, said: "If we are breaking the law then why are we paying VAT?"
Mr Bodley criticised media reports which have portrayed licensees as criminals. He said: "We are not purposely trying to break the law."