Campaigners have launched a petition to call for the Welsh Assembly Government to be given the power to alter the current laws on hunting.
Campaigners want the assembly to be able to change hunting laws
At the Royal Welsh Show on Monday, the Middle Way Group's co-chair Lembit Opik MP and AMs from all parties claimed the fox population was "exploding".
Meanwhile, the show started with judging in the hunter and shire horse section in the main ring.
Officials said 45,000 attended the first day of the show at Llanelwedd.
The Middle Way Group claimed that increasing numbers of animals were being killed by foxes since the ban was introduced.
At present, the assembly government enforces the new Hunting Act but cannot amend it, unlike the Scottish Parliament.
The politicians said the new act, which came into force in February, was making it difficult for farmers to control the fox.
Hunters are allowed to flush the animal out using two dogs, but must they must kill it using a gun.
ROYAL WELSH FACTS
This is the 10st show and 42nd at Llanelwedd
Last year's show made a profit of more than £300,000
There are more than 8,000 entries - a record
There are 42 breeds of sheep
There was a waiting list of 200 for a trade stands
The Royal Andalusian School of Equestrian Art performs for the first time in Britain
Farmer Nerys Evans, from Llanbrynmair, near Machynlleth, had organised the petition after she lost 14 lambs, some chickens and kittens to foxes since the ban.
North Wales Conservative AM Brinley Williams said the very nature of the geography in Wales made it difficult for people to control foxes under the new law.
Farmer Mr Williams said during the lambing season he had he lost between 14 and 18 lambs - together worth around £600. This figure was highter than usual.
Leader of the Welsh Liberal Democrats and Montgomeryshire MP Mr Opik said: "Wales should have the right to amend the legislation.
"There has been an increase in the numbers of foxes and it is making it much harder to control the fox. We feel the assembly government should be allowed to amend in line with Wales' needs.
Horses from the Andalusian school gave a display on Monday
"Farmers are starting to feel the effects of the ban first because of the numbers of sheep in Wales."
Liberal Democrat Montgomeryshire AM Mick Bates, another farmer, said he had losses had been greater than normal during the lambing season.
Plaid Cymru AM Helen Mary Jones said the Labour Government's reasons to ban hunting with dogs were not motivated by animal welfare but by prejudice.
But a spokesman for the League Against Cruel Sports said: "We don't want to see a return to cruelty by the back door.
"I think it would be a retrograde step for animal welfare if the Welsh assembly was given the authority to amend or reverse a law already banning a blood sport."
Meanwhile, the show director admitted he was expecting "bumper crowds" at this year's event.
Harry Featherstonehaugh said queues into the show had not delayed visitors too much.
A record 8,000 livestock entries had been registered for the event.