Dangerous slime should be taken off shelves "straight away" according to a toy shop owner after an investigation raised safety concerns.

Parents have been warned to approach children's slime toys with caution due to a potentially dangerous chemical.

Consumer watchdog Which? found some contain levels of boron more than four times the EU safety limit.

Excessive levels of the chemical could cause vomiting and irritation in the short-term, and also impair fertility, according to the report.

Richard Ray, who manages family-run Nuxley Toys in Milton Road, Gravesend, said: "Whatever this is, unfortunately it’s slipped through the net, and it should be taken off the shelves straight away.

"Everything we have ever sold has always been fully tested.

"We haven’t sold slime for quite a while – lots of people do it, but it’s not something we’ve done."

Which? tested 11 children's slime toys, and found that less than 30% of them met EU safety standards.

All eight of the products found to contain excessive levels of boron were from online retailer Amazon, which has since removed them from the site.

Lee Richman, manager of D&A Toys in Chatham, says the issue isn't a new phenomenon.

He said: "Slime has been around for years, and it’s become a lot more popular in the last year or so.

"Kids love it, and we sell lots of it, but we’ve never had any problems – everything’s been tested.

"There have been similar problems with loom bands and cheap squishy toys in the past, when they haven’t got proper safety checks."

In a statement, a spokesperson for the web giant said: "All Marketplace sellers must follow our selling guidelines and those who don’t will be subject to action, including potential removal of their account.

"The products in question are no longer available."

Of the three products deemed safe by Which? one was from Amazon, one from Smyths and one from The Works.

Parents have also been warned against making slime at home, as some ingredients commonly used to make the toy contain high levels of boron.

For the full report, and safe slime recipes, click here