He made the remarks in the context of reports that the Prime Minister could limit the number of national insurance numbers issued to low-skilled migrants from EU countries in an effort to cut immigration from within the 28-member bloc.
Mr Barroso refused to speak about the proposal specifically on the grounds it had not been presented, but insisted “in principle” a cap on free movement would be in contradiction of EU rules.
He said: “Having said that, full support to all ways of suppressing abuse of benefits because they are against in fact the spirit of our legislation.
“We have to address the abuse cases. I think it is very important to be determined to repress any kind of abuses because there are some kind of abuse of benefits. That is a good point.
“But put in question of principle, I don’t think it is good.”
Speaking on The Andrew Marr Show, Mr Barroso also criticised the comment by Foreign Secretary Philip Hammond last week that Britain was “lighting a fire under the European Union” by holding an in-out referendum on membership.
He went on: “I’m told the Foreign Secretary was the former minister of defence. I think this reference to fire and weapons is more appropriate for defence than foreign secretary.
“It is very important to have a positive tone regarding these issues between Britain and the EU. My advice to all the members... is to have a constructive dialogue, a proper tone.”
He said there was a willingness to constructively discuss the UK’s concerns and insisted the UK would wield more influence on the world stage from within the EU than outside it.
“He [David Cameron] knows well that without the EU, Britain will have less influence,” he said.
Mr Barroso’s non negotiable stance on a cap will come as a blow to David Cameron who has restated his promise to put measures to control EU migration at the heart of his plans to renegotiate the UK’s relationship with Brussels.
But former defence secretary Liam Fox dismissed it as predictable, saying he could have written the script himself.
He told Pienaar’s Politics on Radio 5: “This is effectively the usual line from the bureaucrats in Brussels, which is ‘what the people think doesn’t matter, we will continue down a pre-set path of ever-closer union’.
“It’s this disconnect with the people of Europe, not just the people of Britain, that has produced 30 per cent of MEPs who either want the whole EU abolished or to leave it.”
Conservative Party chairman Grant Shapps said Mr Barroso was “only the latest person from Europe to tell us we’ll never get what we want”.
Cabinet minister Justine Greening told Sky News’ Murnaghan programme that free movement of labour was “never meant to be a totally unqualified principle”.
The International Development Secretary said: “Although we have managed to bring non-EU migration levels down to the lowest level since the 90s, we do need to see action taken in relation to immigration that’s within the EU.
“That means taking a fundamental look at some of the rules that allow unrestricted immigration in a way that we don’t think is sensible.”