An animal charity has said it is "troubled" by plans which could see dogs banned from sports pitches.
RSPCA Cymru has criticised Cardiff Council's plans to bring in a public space protection order (PSPO) against dog owners using marked pitches.
The proposals aim to tackle dog fouling in the city but more than 2,500 people have signed a petition against the ban.
Over the last five years the council has issued 142 fines after rangers saw owners failing to pick up dog mess.
Its proposal would also see on-the-spot fines of up to £100 for dog walkers who let their animals on marked sports pitches, as well as in play areas and school grounds.
Currently, dog owners can be charged up to £80 for failing to clean up mess left in public places, but the move would see penalties issued even if the dog does not defecate on the pitch or it has been picked up.
A number of dog owners are opposing the plan, which has been put out for consultation, saying it would limit where they could walk their pets.
Lesley Brown, 60, from St Fagans, said that the move would be "irresponsible" from the council.
She walks her two black Labradors in Pontcanna fields three times a week at various times of the day.
It is a fenced-off area of Cardiff with sports pitches and would be affected by the plans.
"What the point in having a dog? A dog needs to be healthy and you have the responsibility to keep it exercised," she said.
Ms Brown is also worried that the ban would have an impact on the social benefits of walking her dogs as "it helps people meet one another".
Ben McManus, 33, who runs a Pontcanna dog walking business "WalkWagPlay" with his wife, said their business could go under if the council plan went ahead.
He walks a number of dogs off their leads at Pontcanna fields every day.
"It would have a detrimental impact on every dog we work with," he said.
RSPCA Cymru spokesman Paul Smith said: "We are troubled by any moves from Cardiff Council to ban dogs from marked sports pitches.
"We're proud to work closely with Cardiff Council and urge them not to forbid dogs from marked sports playing pitches, particularly where adequate space for exercise may not be available nearby."
Meanwhile, sports clubs using public pitches have taken to social media to show instances of dog fouling and how they have to clean up before games can take place.
"A small minority of dog owners are utterly selfish," said Ian Titherington after mess was left on a rugby pitch in Cardiff before a under-13 Clwb Rygbi match.
A Cardiff Council spokeswoman said: "Every year we receive a significant number of complaints about dog fouling and out-of-control dogs in public places and while the majority of dog owners are responsible and do the right thing by cleaning up after their dog and keeping them under control there is a minority who cause significant problems.
"The introduction of a PSPO would allow the council to tackle this nuisance so that our public open spaces can be enjoyed safely by everyone."