Almost £1 billion was raised through tax avoidance measures taken by the Government but there was huge potential to raise more money, the TUC has said in a new report.
Tougher measures should be taken, and more staff hired by the Revenue and Customs (HMRC) to tackle the problem, the union organisation argued.
TUC tax adviser Richard Murphy calculated that anti-avoidance measures announced in recent Budgets had raised about £990 million in extra tax revenues.
But the report argued there had been "missed opportunities", including the failure to tackle income shifting - where higher rate tax-payers shift their income to basic rate or non-tax payers.
The TUC accused the Government of backing away from addressing this despite launching a consultation exercise.
General secretary Brendan Barber said: "The Government has made a good start in cracking down on tax avoidance and HMRC has showed real determination in chasing the tax dodgers.
"But there is still huge potential to raise a significant amount of money from a fairer tax system that asks the super-rich to make a proper contribution.
"The best way to tackle the deficit is to get the economy growing again, but there will still be a need to take further action.
"Too many say the next Government will have to make big cuts in vital services or make ordinary people pay more tax. There is an alternative and that is to ask those who did so well out of the boom to start paying a fairer share of tax."