The group estimates more than £17bn is lost to the taxman each year, £12.95bn from accidental or careless evasion and £4.89bn through deliberate evasion.
It argues an amnesty would encourage disclosure and bring thousands of tax dodgers back into sight of HMRC, raising funds immediately and reducing the amount of evaders to chase in future.
A survey by the firm found 96 per cent of accountants would back the idea, while 85 per cent believe offering an amnesty as a final chance to come forward would be a good way to encourage disclosure.
“The reasons for launching a general tax amnesty are numerous, not least the imperative for the government to raise tax revenues in these difficult times of austerity measures,” said CCW’s Sean Wakeman. “HMRC has taken its eye off the ball regarding time limits, and the consequential loss, which could be remedied by a general tax disclosure facility.”
An important part of any campaign would be to reassure evaders that coming clean will not break them financially, he added.