A European Commissioner called David Cameron's migrants crackdown an "unfortunate overreaction" as the Prime Minister attempted to fight off the threat from Ukip.
And Nigel Farage, rather bizarrely, accused him of "trying to shoot Ukip's fox with a catapult made from soggy spaghetti."
Nick Clegg has backed the pledge to stop new arrivals from the EU getting out-of-work benefits for three months.
On the Today programme, EU Commissioner for employment Laszlo Andort was given a tough ride by John Humphreys as he attempted to hit back.
Andort said it could lead to a "slippery slope" where each country tries to manipulate the rules for its own advantage.
Some Tory MPs are increasingly worried about the end of visa restrictions on Romanian and Bulgarian nationals from January.
- SEE ALSO: Tutu fears return to Enoch Powell language over immigration
Cameron also demanded wider EU reforms for the future - suggesting labour movement from countries joining the EU could be limited until they hit a certain level of GDP per head.
Cameron said: "We are changing the rules so that no one can come to this country and expect to get out of work benefits immediately; we will not pay them for the first three months."
"If after three months an EU national needs benefits - we will no longer pay these indefinitely. They will only be able to claim for a maximum of six months unless they can prove they have a genuine prospect of employment.
Cameron said migrants found begging or sleeping rough could be deported.
"They will then be barred from re-entry for 12 months, unless they can prove they have a proper reason to be here, such as a job," he added.
Deputy Prime Minister Nick Clegg insisted his Liberal Democrats were fully signed up to the rule changes - although senior sources stressed that the post-2015 ideas had not been agreed. "These are sensible and reasonable reforms to ensure that the right to work does not automatically mean the right to claim," Clegg said.
"Other countries in the EU already have similar policies and are considering the case for going further - unfettered access to benefits across the member states simply does not exist.
"Anyone who believes we are better off as an outward facing nation should support these changes. If we don't get to grips with these issues, pro-Europeans surrender the debate to the UKIPs of this world."
On Today, Farage said: "I wouldn't call that tough. I would say that we are still being far too generous even if he does have the guts to put this in place."
He later tweeted his spaghetti jibe at the Prime Minister: