David Cameron is being offered an "emergency brake" that would mean EU migrants can be barred from claiming benefits for four years when public services are under strain, it has been claimed.
European Commission president Jean-Claude Juncker is set to give details of the proposal when the two men hold talks on the membership renegotiation in Brussels tomorrow, according to Reuters.
It is not clear whether EU officials would need to give permission for the mechanism to be used.
The idea, which the Prime Minister is also thought to have discussed with his Czech counterpart in Prague last week, has apparently gained traction as Mr Cameron struggles to finalise a deal in time for a key summit next month.
Mr Cameron cancelled a visit to Copenhagen tomorrow in order to meet Mr Juncker in Brussels, and is due to have a working dinner with European Council president Donald Tusk in Downing Street over the weekend.
The Prime Minister will then fly to Hamburg on February 12, where he will have the opportunity to discuss his plans with chancellor Angela Merkel as he delivers a speech on EU reform to the annual St Matthew's Day banquet.
Mr Tusk is due to publish "concrete proposals" for dealing with the UK's demands within the next couple of weeks, ahead of a crunch summit on February 18-19 at which Mr Cameron hopes to secure agreement with the 27 other EU leaders on a package of reforms.
Downing Street denied that the flurry of meetings were an indication of concern within Number 10 that the PM's timetable for an in/out referendum may be slipping.
Foreign Secretary Philip Hammond has admitted that a referendum this summer will be difficult if no deal is struck at the February summit, and "impossible" if it is not agreed at the following meeting in March.
Mr Cameron has mooted a four-year ban on migrants claiming in-work benefits in a bid to reduce the 'pull factors' of the UK welfare system, but other countries have made clear they regard the proposal as discriminatory.
A spokesman for the Prime Minister declined to comment on the "emergency brake" plan, insisting there would be no "running commentary" on the renegotiation.
He said "a number of options" had been put forward. "These discussions will continue. There is still more work to do and hopefully we will get the reforms we want to see," the spokesman said.
Arron Banks, co-founder of the Leave.EU campaign, said: "People watching the slow-motion disaster overtaking Europe don't want an emergency brake on immigration, they want control of the steering wheel so we can avoid the car crash up ahead.
"We know the Prime Minister understands how inadequate this new proposal is himself because he dismissed it as 'some arcane mechanism which would probably be triggered by the European Commission and not by us' two years ago."