Police opened a probe after a brawl broke out on March 19 — when Spain celebrates Father's Day — at a match involving 12- and 13-year-olds on the Mediterranean island of Mallorca.
A video captured by a mobile phone which has been seen over 100,000 times on YouTube shows adults shouting, kicking and taking swings at each other.
“There are children!” a woman can be heard saying in the background.
Another video that emerged earlier this year showed two fathers squaring off at a stadium on the island of Gran Canaria.
One of the men was admitted to hospital and had to have eye surgery, according to sports daily Marca.
The videos have outraged Spaniards and thrown a spotlight on the responsibility of clubs for the behaviour of their young players' parents.
The match in Mallorca was suspended and the two clubs face a fine of up to 1,500 euros ($1,600).
“The fines are a joke,” the president of the referee committee on the Balearic Islands, Bartolome Riera, told AFP.
“If it really hit the pockets of clubs and parents, it would weigh more.”
'Everything is allowed'
Angel Andres Jimenez, a former referee who now lobbies against violence in sports, said the example set by adults at youth matches “is terrible”.
“We need to re-educate youths and that is a lot of work. Because what they have seen is the behaviour of their parents, people who are a role model to them.”
“A lot of parents have a vision of sports where everything is allowed,” said David Garcia, a sports psychologist who co-authored a manual aimed at parents.
“The main problem is a lack of empathy by parents towards their children. They don't think of what is good for them, they want to make the dreams which they were not able to achieve come true.”
While the problem exists in other countries, Garcia complains that in Spain action is only taken when incidents make it onto television.
Sergio, a football referee who preferred not to give his last name, said the behaviour of the public at amateur youth league games “is terrible”.
“Children hear their parents insult and threaten the referee and the opposing side,” he added.
During the 2015-16 season 218 amateur football matches in Spain were marred by violent incidents, including 58 youth matches, according to the government sports council (CSD).
Referees say the figures do not reveal the magnitude of the problem.
“The violence starts with insults, denigration, threats. This is what happens in the vast majority of matches,” said Jimenez, the anti-violence campaigner.
“If a Spanish referee calls the police, it is because he fears he will be hit,” added Sergio, the referee who wants to remain anonymous.
Both men say parents should be slapped with penalties as soon as they become verbally aggressive.
They accuse amateur clubs and Spain's 19 regional football clubs of being too lax.
“These are small clubs with small followings. They are not going to act against their supporters who are their source of money,” said Sergio.
He said he is often pressured by his superiors when he cracks down on aggressive behaviour.
The president of Spain's government sports council, Jose Ramon Lete, has called for a conference against violence in the wake of the videos showing parents brawling at youth matches.
But unlike in the professional football league, where violations of rules are punished every month, in regional amateur leagues rule enforcement is haphazard.
Each region has its own policy. For example in February the federation of the southeastern region of Murcia launched a campaign encouraging parents to greet each other before matches.
Riera proposes installing cameras at all football stadiums.
Garcia is calling for a campaign to educate coaches as he is pessimistic that clubs will take fresh action.
“They will try to solve this with the means that they have already, and are going to try things that have not worked in the past,” he said.