The 23-year-old wrote on Facebook: "A one-year-old boy had messed all over the play area and apparatus due to him being unwell with some kind of sickness bug. It was left until another child got covered in it."
The mum said the centre sent a young member of staff to clean it up, but claimed they did not have the correct utensils to do it "efficiently and safely".
She continued: "We thought that was the end of it until a woman found her daughter and my daughter covered in even more faeces.
"Luna had some on her top but the other little girl was caked in it, the mother just threw the clothes away then and there.
"Children were still playing in the play area.
A spokesperson for the play centre in Camberley, Surrey denied mum Sian's claims Credit: google "No one was being informed of what was happening so my mum had to tell everyone to get their children out.
"I am not looking forward to how ill my children are now potentially going to become, and this could have been prevented if the women who worked there cared a bit more about the safety of the children they're there to serve."
Magic Castle denied the claims.
A spokesperson said: "We take all incidents at the Magic Castle extremely seriously, especially hygiene, and have worked very hard with Surrey Heath [Environmental Health] to ensure the correct procedures are followed.
"As soon as the incident was reported to a member of staff, they acted immediately. The affected main area was cleaned using the chemical Oxivir, which is the correct cleaning method for this purpose.”
Sian also claimed her mum was refused a refund after she asked for her money back.
In response, Magic Castle said: "Any customer at the time of the incident who reported their child coming into contact with the spoilage and requested a refund was refunded in full."
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