The 21.6% failure rate is higher than in other European countries that do MoT tests every four years, such as France with a 5.61% failure rate and Switzerland with 17.5%.
In countries that also test for the first time at three years, failure rates are far lower than in the UK (Germany 4.8% and Austria 10%).
IAM Trust is waiting for a Government consultation that was due almost a year ago into the viability of delaying the first MoT test until vehicles are four years old, then having them every two years, instead of the current system of the third year after registration and then every year after.
Neil Grieg, IAM trust director, said: “The high UK failure rates may argue against relaxing our MoT testing regime from three to four years on road-safety grounds.
But do we have the full picture?”
“We want to know where on earth the consultation is. It took us months to acquire what we wanted using the Freedom of Information Act.
There are a lot of questions that need to be answered.”
A Department for Transport spokesman said that while reducing test frequency could theoretically save motorists money, it was likely to result in more accidents due to unsafe vehicles being on the road.
He said: “There has been a delay with the consultation, but given the potential serious implications for road safety it is important we get the decision right.”
“It is also inappropriate to make simple comparisons of MoT failure rates across Europe, because there are differences in the way tests are carried out and differences in the way that results are recorded.”
The consultation is expected to be published within the next two months.
Brian Spratt, Automotive Distribution Federation chief executive, said the delay with the MoT consultation was preventing businesses from planning their future.