A boy of nine broke both his arms after falling off a climbing frame at the centre of safety fears.
Louise Millar is now considering suing Brighton and Hove Council over the incident.
Her son Ryan will be in hospital for the next four weeks.
He was playing on the climbing frame in Stoneham Park, Hove, when he lost his grip and fell a few feet to the ground.
He used his arms to break his fall and broke both of them.
The climbing frame is due to be dismantled because it does not meet current safety standards, although the council says the shortcomings would not have caused the fall.
Miss Millar, 31, is angry that no signs were put up to warn children and parents.
Ryan, who goes to West Hove Junior School, will be in traction for up to four weeks and will then have his arms put in plaster.
Miss Millar, of Livingstone Road, said: "I know the climbing frame needed some sort of improvement, so why weren't there any signs around it?
"I have phoned a solicitor because I want to take legal action against the council."
A Brighton and Hove Council spokesman said: "Our safety concerns were about bolts sticking out of the structure, not the possibility of a child falling from the frame which could happen with even the safest equipment.
"This one had the right so-called 'safer-surfacing' on the ground.
"We cannot confirm this incident happened as described.
"If it did, it is very odd that nobody seems to have reported it to us, especially if they are thinking of taking legal action."
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