The influential Commons Public Accounts Committee of MPs has apologised to motorcyclists after wrongly suggesting 40% of motorbikes were untaxed.
Motorcyclists pay up to £64 a year in vehicle excise duty
Committee chairman Edward Leigh blamed the error in last month's report on the Department of Transport, saying it now estimated the figure at 9.8%.
At the time he accused motorcyclists of "cocking a snook at the law".
Motorcyclists' groups said transport chiefs should be "embarrassed" - and said the estimate was still too high.
The committee's report found that enforcement of road tax on motorbikes was difficult because roadside cameras had been unable to read their number plates from the rear.
It was also hard for the police to detain motorcyclists as they could easily turn round and drive off, the report said.
At the time, Mr Leigh recommended "more severe measures such as impounding unlicensed motorcycles", adding: "Large parts of the biking community are cocking a snook at the law."
This provoked outrage among motorcyclists.
Following the realisation that the figures upon which the report was based were wrong Mr Leigh said: "I apologise to motorcyclists and wish to offer an explanation."
He said motorcycle users had been "concerned" over the findings of the report "which were based on national statistics provided by the Department for Transport".
Mr Leigh added: "The department did not, however, give us all of the information we needed.
"It did not make the committee aware at our hearing last year that a new, more accurate methodology was already being used to produce estimates of rates of road tax evasion for the year 2007-08, nor that it could have implications for the accuracy of the previous year's estimates upon which the committee had to rely."
David Taylor, chief executive of the Motor Cycle Industry Association said "The motorcycle industry has said for years that the methods of calculating VED evasion were deeply flawed, but we have been consistently ignored. In fact, we still say that the methodology is wrong."
He added: "The DfT should be embarrassed and should apologise to the vast majority of powered two-wheeler riders who clearly do pay VED."
A Department for Transport spokeswoman said: "It was only known that the 2007 estimates would not be comparable to earlier estimates after detailed analysis of video recordings showed that misread registration marks tend to push up evasion estimates.
"This quality assurance stage took place after the PAC hearing."