A spokesman for the council said the filtration system is not designed cope with ‘contaminants’ like sun cream.
Furious residents took to social media, condemning the decision as ‘ridiculous beyond belief’ and ‘a joke’.
The Forum Fountains have been switched off until further notice the council said, adding that it was ‘disappointing’.
In a statement the council said: “The Forum Fountains in Horsham is a water display and not a splash pad.
“While people may choose to play in the display on occasions, the large number of people doing so in hot weather leads to large quantities of contaminants, such as sun cream, entering the filtration system.
“The pumps and filters are not designed to cope with the feature being used as a play area.”
Trafalgar ward councillor Christine Costin said turning off the fountain risks people losing interest in the town.
She added: “It’s a bit sad particularly when you have got this lovely heatwave.
“Water features are very much part of Horsham’s attraction and that the more we take them away people are going to lose interest in the town.
“We don’t want that so attention needs to be put to the ‘dancing waters’ to get them dancing again.”
But she warned that a slippery surface meant the fountains could be dangerous if people bathe in it.
She said: “I don’t really think children should be playing in it too much.
“I can’t say I approve of loads of people [using the fountain]. I do think it could become dangerous.”
Councillor Costin suggested putting up signs warning people of the danger and said the council should consider making the fountain ‘more screened off’.
She added: “There should an indication that it’s not advisable to play in it. Watch it by all means.
“It just makes you feel good, it cools you down just to look at it.
“It’s for enjoying the general ambience. I hope that it will be stuck back on with suitable messages - the surface could become slippery.”
It would be ‘a shame’ to stop people walking through the fountain according to councillor Costin but she advocated it if it was the ‘only way’ to get the fountains back in action.
She said ideally the council should make the fountains safe for people to play in but she did not know how much that would cost.
Councillor Costin added: “For a while I think it would be better just to have some notices there to say to parents it’s not safe for your kiddies to use because the surface becomes slippery.
“You have got to do something. The public needs to respect water.”