Warning over 'lethal' quad bikes
Sam Whyles died in a quad bike crash in the grounds of his parents' home
Safety groups are warning parents about the dangers of buying quad bikes as Christmas presents.
The Royal Society for the Prevention of Accidents says quad bikes can be lethal and fears parents may be tempted to buy cheaper models on the internet.
More than 1,000 people are seriously injured on them every year, with deaths averaging two a year.
Families of those killed in accidents are calling for laws making helmets for quad bike riders compulsory.
Amii Groves, whose 25-year-old brother Lee was killed on a quad bike in July, said: "It's not illegal to not wear a helmet on a quad bike."
She said of her brother: "He did have one but he didn't wear one that day. We are devastated. He's dead because of the quad."
Two months later, 12-year-old Sam Whyles died in a quad bike crash in the grounds of his parents' home in Corsham in Wiltshire.
The bikes - more properly known as All Terrain Vehicles (ATVs) - are popular among motor sports enthusiasts and dealers insist they are safe if used properly.
Last year about 12,000 quad bikes were sold through dealers, who provide free training.
Richard Leonard, from Honda UK, said: "These are not a toy, they are designed for work on the land and if used properly they are quite safe."
Only specially adapted vehicles can be used on public roads but there is no legal requirement to wear a helmet on a quad bike on or off road.
Peter Cornell, of the Royal Society for the Prevention of Accidents, said the bikes can be lethal and he was concerned about people buying them from people who were not from a proper dealership.
"I think what the government does need to look at is that they are so cheap. You can buy them off the internet for a couple of hundred pounds," he said.
"Maybe we need to look at how easily they are supplied. If people are buying these off the internet, not from a proper dealership, they are not going to get the safety advice that they need to get."
Andy Heitman, from the European ATV Safety Institute, said there were concerns people who knew little about the product or the potential dangers would be selling them at car boot sales and in pub car parks.
A Department for Transport spokesman said quad bikes must meet safety standards and be registered, taxed and insured if used on public roads.
He said drivers must also hold an appropriate licence and were advised to wear a helmet.