Worried parents have expressed concerns over an online game which allows strangers to send messages to children.

Roblox, which markets itself as the number 1 gaming site for kids and teens, invites children to “create adventures, play games, role play and learn with their friends in a family-friendly, immersive 3D environment.”

Kids make an account using their phones, tablets or computers and then have access to more than 22 million games in virtual reality worlds where they make their own characters.

A chat facility on the site means strangers can message kids directly and chat to them - with no way to screen contacts or block messages.

While under-13s who register for the site can only chat to their approved friends list, there is no verification of date of birth when making an account and youngsters can easily gain access to the full chat facility.

There’s been a wave of reported cases of adults using Roblox to pose as children and send them lurid messages, with one eight-year old from Sunderland even receiving requests to meet up.

Mum-of-three Rebecca Thomson, 36, runs parenting group Greenwich Mums and says she would be sickened if her seven-year-old twin girls were targeted through Roblox.

She said: “I would be horrified if my child received explicit messages from an app that markets itself to children in this way, it’s a honey pot for weird people.

“People out there will try any way they can to access children and that access has gone up exponentially with the rise of technology.

“It’s no longer just weird men or women sat outside schools in their cars we have to worry about, there is clear potential for grooming here.

“If they are promoting this app as the number one gaming site for kids and teens then they need to take responsibility for their safety, but as parents we do too.

“Websites can be blocked at an IP level through your home internet system, meaning kids can’t access them.

"We need to actively seek out these sites and stay ahead of the game to protect our children.”

Kathy McGuiness, 44, from Carshalton, is also worried about her children accessing Roblox.

The mum-of-four started a national campaign called Child’s Eye Line which promotes internet safety and helps to protect children online.

She said: “I’m very concerned to hear about Roblox.

“I have a daughter who has just turned 12 and I won’t let her have a smartphone because of readily available apps like this, but she’s under so much pressure from friends to get one.

“There’s a complete lack of control. You think your kids are going to get bullied or whatever outside but actually they’re in more danger sat in their own homes being targeted on the internet by strangers.

“Kids know more about the internet than us now and it’s a scary thing because parents are out of touch.

“Young children should not be able to access smartphones and it’s something the government need to regulate and parents need to be more aware of, because children are suffering and we can’t control what they are exposed to.”

A Roblox spokesman said: "The safety of our community is a top priority and we’re constantly assessing and improving our trust and safety measures.

"There are several safeguards in place to protect our users that utilize current technology and human oversight.

"We have instituted a best-of-breed, third-party software system created specifically to find offensive language and flag it.

"For users that are under the age of 13, these filters are set to block any sharing of personal identifiable information.  We continually fine tune this software to detect and block new and creative ways to message inappropriately. 

"We also scan the site multiple times daily to ensure that none of our users are having inappropriate web technologies used to track or identify them.

"All accounts for users that are under the age of 13 are set to only communicate with friends. Only friends in the approved friends list can personal message, invite another user into games, or to join a VIP server."