The 32-year-old, who rode to glory with Team Sky last month, believes cyclists have “no reason not to” wear a helmet on UK roads.
Unlike for motorcyclists or moped drivers, there is no compulsion in UK law for cyclists to wear a helmet while out on the roads, despite it being recommended under the Highway Code.
Late last year, the government revealed it will look at the issue as part of a wider review into cycling safety, although cycling campaign groups oppose making helmets mandatory.
In an interview with the Sunday Times magazine, Thomas spoke of the UK’s recent cycling boom, which has coincided with British riders winning the Tour de France six times in the last seven years, including his own somewhat surprising success.
He said: “Things have improved a lot since 2008 and 2012, after the Olympics, when cycling really caught on.
“When I was a kid I was always being beeped and told to get off the effin’ road. The problem is that cyclists and drivers see each other as enemies.
“A cyclist can get cut up by a car and the driver has been an idiot, but 10 minutes later that cyclist is jumping a red light. You’ve got to share the road.
“London is different. I’ve never ridden a bike in London, apart from in a race. I’ve watched from a taxi and it does seem a bit crazy.
“I would certainly make helmets compulsory. I always wear a helmet, I’ve put on a helmet more times than I’ve buckled a seatbelt.
“Helmets have come on a lot – well ventilated, not too hot, you don’t look stupid – no reason not to.”
However, Thomas’s views contrast with those of fellow Olympic cycling gold medallist Chris Boardman, who has previously stated making helmets compulsory “isn’t even in the top 10 things that will really keep people who want to cycle safe”.
Boardman’s mother, Carol, died of her injuries after being hit by a truck while out cycling in North Wales in July 2016.
He has recently attacked the government for raising the issue as part of its cycling safety review, pointing to evidence that cycling use drops where helmets are required by law.
Boardman wrote in an article last year: “In the UK 1 in 6 deaths – nearly 90,000 per year – is as a result of physical inactivity related disease including diabetes, heart disease and cancer.
“Clearly, any measure proven beyond doubt to reduce peoples likelihood to travel by bike, will almost certainly kill more people than it saves.”
His stance is shared by Cycling UK, the national cycling charity.
In 2016, 18,477 cyclists were hurt in reported road accidents, with 102 deaths and 3,397 seriously injured.
Earlier this month, the government announced plans to consult on introducing a “death by dangerous cycling” offence following the high-profile death of mother-of-two Kim Briggs.
But the Conservative Party were forced to apologise for a social media post that stated the “most vulnerable road users” need protection from “dangerous cycling”.
Ministers were also accused of focussing their time on the smaller proportion of people killed by cyclists, rather than conducting a full review of traffic offences.