The Work and Pensions Secretary insisted the Prime Minister deserved credit for his tough stance on the EU budget and repatriating powers from Brussels.
However, Mr Duncan Smith came as close as any Cabinet Minister to hinting Britain could thrive outside the EU if it so wished.
After leading Tory rebel Mark Reckless suggested at least one member of the Coalition Cabinet had toyed with resigning ahead of last week's House of Commons vote, Mr Duncan Smith, a noted eurosceptic, made that clear achieving an inflation-only rise – about 2% – at a crunch EU summit later this month would be a good result.
He said: "We are here right now trying to restrict the amount of money that goes to the European budget.
"He [Mr Cameron] would love to come back with a real-terms cut; I would love him to do it.
"But I just honestly feel that sometimes we do not give enough credit to him – the first man to veto a European treaty.
"He has told us he will veto something that he cannot bring back to the British Parliament.
"These are strong words compared to the last Government and even Governments before when we saw budgets rise under the last Government; we saw them lose half our rebate.
"The Prime Minister has been quite tough and quite strong on this."
The Secretary of State refused to state whether he personally wanted to see Britain leave the EU, but made clear the country could thrive inside or outside the grouping.
"I am an optimist on the UK. We are a member of the EU, that gives us benefits, but we have to figure out where that is going."