Ictu has called for stricter rules for tax advisers to prevent "abusive tax planning".
The call comes in the wake of yesterday’s report that the Revenue netted up to €700 million in special investigations into tax evasion last year.
Ictu general secretary David Begg said: "The success of the Revenue Commissioners should not disguise the fact that there is also a very high level of tax avoidance.
"A significant number of high net worth individuals are able, with the help of advisers and an accommodating regime of tax shelters, to pay little or even no tax, in some cases," he said.
Although the Government had to account for the nature of the tax regime, the role of tax advisers was subjected to comparatively little scrutiny, he added.
"Apart from the banks, nobody in this profession has ever been called to account, either morally or legally, for facilitating the abuses which have been revealed in recent years," Mr Begg said.
"By contrast, in the US and some other countries tax advisers involved in flagrant tax abuses can be hit with huge penalties.
"This should also be a policy objective for Ireland. One the main arguments advanced against making wealthy people pay at least a minimum amount of tax is that it would encourage more aggressive tax planning. A stricter legal framework for tax advisers might obviate that difficulty, " he said.