Thousands of supporters across England and Wales watched the first 250 Boxing Day hunt meetings since the Hunting Act banned hunting wild animals with dogs.
The Countryside Alliance says the Hunting Act is not working
The League Against Cruel Sports said the crowds were swelled by first-time spectators opposed to animal cruelty.
The RSPCA said it believed many hunts had successfully converted to drag or trail hunting, using artificial scents.
But the International Fund for Animal Welfare said it would observe hunts and film suspected breaches of the law.
Hunts are no longer allowed to use dogs to chase down foxes, but are instead supposed to use techniques such as drag hunting, where dogs set off on the trail of a scent laid about 20 minutes in advance by a runner or rider dragging a lure.
League Against Cruel Sports head of public affairs Mike Hobday said: "We are getting reports of a number of people who are saying they would not have turned out for the hunt if they were chasing foxes and they thought animal cruelty was going to be involved.
"There is a whole group of people in the countryside who do not believe in cruelty, who do not believe it is right to chase foxes and who are free for the first time to get involved with hunts."
There was no "mood amongst the public to think that chasing and abusing animals for entertainment is acceptable for a modern society", he added.
The league says it is happy for the hunts to meet as long as they stay within the law.
"If they want to dress up in ridiculous clothes, drink and ride across the countryside we have no objection to that," Mr Hobday said.
"What we object to is the cruelty."
But more than 40% of hunts in England and Wales have had "credible allegations of law-breaking made against them", the league estimates.
It blames Countryside Alliance members for "a catalogue of misdemeanours" involving a "disturbing level of abuse, intimidation and trespass" since the first hunting season to follow the Hunting Act began on 5 November.
"Just as the Theft Act did not stop burglary, the Hunting Act cannot stop cruelty - what is needed is for people to obey the law," Mr Hobday told BBC News.
The league promised to continue monitoring hunts to ensure no foxes were killed illegally.
But former League Against Cruel Sports director Jim Barrington, who was among 4,000 supporters at the Beaufort Hunt in Gloucestershire, said: "I, and a number of others, have come to the conclusion that a ban is not the right way forward.
"The Hunting Act is a ridiculous piece of legislation. It is unenforceable and will cause greater animal suffering."
Beaufort Hunt secretary Nigel Maidment said: "More people than ever are prepared to give us their support.
"People want to see an end to this stupid act."
Caroline Black said the 2,000 supporters at the Bicester with Whaddon Chase Hunt had doubled last year's turnout.
Campaigners say more than 40% of hunts may break the law
Hunt secretary Robert Valance said they would be watched closely by Thames Valley police and should stay within the law.
The Countryside Alliance said a poll showed that only a third of people thought the new legislation was working.
The survey, which was carried out by ORB for the Countryside Alliance, asked: "From what you know do you think the Hunting Act is working, i.e. is it preventing hunting of wild mammals with dogs?"
Nearly three-fifths (59%) of the 1,004 respondents said no, 34% said yes, while seven per cent said they did not know.
Simon Hart, chief executive of the Countryside Alliance, said: "This law is not a year old but already people have come to understand what hunts across the country have known from the start. Quite simply the Hunting Act isn't working.
"It is a bad law riddled with inconsistencies, and its effects are entirely negative.
"It is a blatantly discriminatory piece of legislation which threatens jobs, communities and the countryside as a whole, while doing nothing for the welfare of the quarry species," Mr Hart said.