The Council of Europe claims the handouts given to Britain's jobless are 'manifestly inadequate'.
Ministers have been told they are in violation of the European Social Charter - potentially opening the door for claimants to take the Government to court to get more money.
But ministers say obeying the diktat from the Council, which oversees the controversial European Court of Human Rights, would cost the UK billions of pounds and plunge efforts to reduce the deficit into chaos.
To comply, Jobseeker's Allowance (JSA) would have to be hiked by £71, from £67 to £138 a week.
Last night Work and Pensions Secretary Iain Duncan Smith accused the Council of Europe of 'lunacy'.
He told the Mail: 'This Government has made great strides in fixing the bloated welfare system we inherited from Labour. It's lunacy for the Council of Europe to suggest welfare payments need to increase when we paid out £204billion in benefits and pensions last year.'
The Council said Britain had signed up to the Social Charter, which is 'a legally binding economic and social counterpart to the European Convention on Human Rights'.
The charter sets out a level of income which certain key benefits - including the JSA, Employment Support Allowance (ESA) and State pension - must provide.
Britain's JSA, ESA (both £67 a week) and pension (about £102) all fall well below the £138 a week, or £596 a month, that the Eurocrats have set as the benchmark.
Because all three are below a second threshold of £110 a week, they are rated 'manifestly inadequate'.
The Council cannot directly punish the UK for these 'violations', but its officials say national courts refer to these international standards when deciding on relevant cases.
This means benefit claimants could try to use the Council's condemnation to bolster their case for more money.
Tory MPs last night reacted with anger.
Douglas Carswell, Conservative MP for Clacton, said: 'We simply cannot afford to spend more money on welfare.'
Comment: No, but so far you've spent almost £2 trillion on giving the banksters social welfare...
Philip Davies, Tory MP for Shipley, said: 'The Government can no longer stand by. They have got to say, "We're sick to the back teeth of this interference, we're going to withdraw from the European Convention of Human Rights".'
Comment: They might as well; the UK govt never adhered to it anyway.
'Human rights? But we're psychopaths! What care we for humans' rights?'
Last night a spokesman for the Council of Europe said the committee is well aware that changes in benefit payments 'can be extremely difficult to bring about, certainly in the short term'.
The numbers seem wrong to me my not by much.
For example, JSA is:
Age: 16 to 24 £56.80
Age: 25 or over £71.70
Couples (both aged 18 or over) £112.55
Lone parent (18 or over) £71.70
Lone parent (under 18) £56.80
So £56.27 is what each person in a married couple get.
To claim JSA you are required to have an internet connected PC OR visit the Job Centre every working day. The former is typically cheaper so real rates are much lower. Further as utility bills must be paid the amount available for food is negligible. Recently my gas and electrictiy bills averaged £40 per week. Water rates £14 per week. Then there is council tax £30 at week. If I was on JSA I would have MINUS £35 ($50) a week before food. Government ministers like Edwina Curry talk of people living the life of Riley on the vast handouts they are given. They are planning to welfare spending by a further £25 bn this year.