A Labour government could withhold out-of-work benefits from European Union (EU) migrants until they have paid into the system through National Insurance, shadow work and pensions secretary Rachel Reeves has said.
Ms Reeves' comments come a day after shadow chancellor Ed Balls indicated a shift towards a harder line on immigration, saying that he backs "fair movement, not free movement" for EU citizens coming to the UK.
Their interventions - part of a summer offensive ordered by Ed Miliband to draw clear lines with the Conservatives in the run-up to next year's general election - will be seen as an effort to win support back from the UK Independence Party, which has been picking up on concerns about immigration to eat into Labour's traditional working-class vote.
Speaking to the Sun on Sunday ahead of a speech on Tuesday, Ms Reeves said migrants from Europe could be denied benefits altogether until they have worked and built up National Insurance contributions.
"It isn't right that somebody who has worked hard all their lives and has contributed to the system is entitled to only the same as somebody who has just come to this country, so we need to look at that," said the Leeds West MP.
"It shouldn't be that you can draw on the system without having contributed."
The proposal risks putting the UK at loggerheads with Brussels unless it was also applied to British citizens.
But Ms Reeves said: "There does need to be reform of the system.
"Whether that means having to work with partners in Europe to reform the system, or changing our system so it is better based on contributions, we need to make those changes."
She is expected to use her speech to accuse Work and Pensions Secretary Iain Duncan Smith of presiding over "a culture of waste, write-offs and failure", including £134 million on the flagship Universal Credit, £140 million on Personal Independence Payments and £27 million on a scrapped web-based service called My Benefits Online.
Yesterday, Mr Balls indicated that he wants to see change in the EU rules guaranteeing the right for citizens of member states to settle, work and claim benefits in other parts of the union.
The shadow chancellor told the Daily Telegraph: "We have lots of rules that fetter movement. We think you should toughen up those rules.
"You shouldn't be free to work in Britain and send back tax credits. You shouldn't be free to come to Britain and be unemployed. You shouldn't be free to come to Britain as soon as your country joins the EU."
He added: "What I want is fair movement, not free movement. It needs to be fair to people who come and work here and fair to people in this country."
A Conservative spokesman said: " No-one will be fooled by Labour's latest welfare gimmick. They have no credible plan to secure change in Europe and lost the right to comment on welfare after they created a culture of dependency and left an extra 500,000 people unemployed.
"Only the Conservatives have a real plan to put Britain first and ensure our welfare system rewards hard work."