Migrants could be forced to sign in at police stations to keep track of their movements so they can be deported if they are unemloyed after six months in the UK.
The Telegraph reported that polic checks were being considered as a way to ensure the Tories' new proposals for reducing migration could be physically enforced.
The Prime Minister signalled in a speech yesterday that those with jobs will only receive in-work benefits, such as tax credits, and social housing once they have been in the UK for four years.
No child benefits or tax credits for children living elsewhere in Europe will be paid out, regardless of how long an EU migrant has paid into UK coffers under the plans. He hinted he was prepared to leave the European Union if the plans were not approved.
A Cabinet minister told the Telegraph migrants could be forced to register with police on arrival in the UK, allowing the authorities to check whether they had found work after six months.
“We are considering all options,” the Cabinet minister said. “And requiring migrants to sign in and register at police stations is one of the things we are looking at.”
The plan is a "row back" from Cameron's previous intention of imposing a migrant cap, which would have had vast implications for the freedom of movement principle in the EU.
The Guardian reported that German Chacellor Angela Merkel had personally warned Cameron that idea was a non-starter if he wishes Britain to remain a member state.
“The German government has in the past again and again underlined the significance of the principle of the free movement as it is anchored in the EU treaties. It is important that Cameron commits himself to this central pillar of the EU and the single market," a German government spokesman said after the speech in Staffordshire.
But Foreign Secretary Philip Hammond has denied that Cameron "backed off" in the face of pressure from Merkel, but acknowledged that ministers had consulted with other EU member states ahead of Cameron'smuch-trailed speech yesterday.
"I don't think that is right. What is right is that we have sought to work with our partners in the European Union to understand the best way of delivering a reduction in immigration numbers from the EU in to the UK," Hammond told the BBC Radio 4 Today programme.
Hammond, however, insisted that with "well over" 400,000 EU nationals currently claiming UK benefits or tax credits, the proposed changes would make Britain a "significantly less attractive destination" for migrants.
"That will get the numbers down," he said.
He confirmed that some of the measures, which the Conservatives say they will implement if they regain power in the general election in May, would require changes to the EU treaties, which, in turn, would need the agreement of other member states.
"They will form part of the broader negotiation that we will have with the other members of the European Union about reform of the European Union ahead of the referendum which we are giving to the British people in 2017," he said.
The Czech Republic's Europe Minister responded to the PM’s immigration speech by posting a picture of Czech pilots serving in the RAF during the Second World War.
Tomas Prouza posted the picture on Friday, having been upset by Cameron’s suggestion that EU immigrants should only be allowed to claim welfare after they had been in the UK for four years.
He responded by posting the following tweet, with the words: "These Czechs 'worked' in the #UK for less than four years. No benefits for them?"
This followed an earlier Tweet by Prouza in which he said: "Cameron's speech on migration: taxing people according to their nationality? What other criteria will come next?"
Prouza’s sentiments were echoed in Warsaw, with the Polish Prime Minister Ewa Kopacz releasing a statement that read: "Poland will not agree to changes undermining the principles of the EU's single market, specifically the free movement of people."
The Tory leader's speech marks an attempt to regain the agenda after embarrassing official figures showed net migration to Britain is higher than it was when the coalition came to power, leading experts to conclude that his promise to cut migrant numbers was "dead and buried".
Unemployed Europeans heading to Britain to find work will have six months to find a job or they will be kicked out, he said in a keynote speech on immigration.
Cameron's proposals may be hard to enact as the European Parliament's President Martin Schulz has warned that they would need the approval of all the rest of the European Union's member states.
"Let's be clear," he told the Huffington Post UK. "If they [Cameron's proposals] are not in the interests of all 28 member states, we will not get it [any re-negotiation]."
Schulz said that the UK was not part of the Schengen Group [26 European member states without border control] or in the euro, and the rest of the member states would only look at any new proposals for change once they were concrete.
"He says ‘our relationship with the European Union’, well, this is a relationship with yourself. The UK is a member of the EU. I don’t negotiate about my relationship with myself, it’s a little bit strange."
The Prime Minister insisted the package of measures he is unveiling will mean Britain has the toughest welfare system for EU migrants anywhere in Europe.
He said: "People have understandably become frustrated. It boils down to one word: control. People want Government to have control over the numbers of people coming here and the circumstances in which they come, both from around the world and from within the European Union. And yet in recent years, it has become clear that successive Governments have lacked control. People want grip.
"I get that.They don't want limitless immigration and they don't want no immigration. They want controlled immigration. And they are right. Britain supports the principle of freedom of movement of workers. Accepting the principle of free movement of workers is a key to being part of the single market.
"So we do not want to destroy that principle or turn it on its head. But freedom of movement has never been an unqualified right, and we now need to allow it to operate on a more sustainable basis in the light of the experience of recent years. My objective is simple: to make our immigration system fairer and reduce the current exceptionally high level of migration from within the EU into the UK.
"We intend to cut migration from within Europe by dealing with abuse; restricting the ability of migrants to stay here without a job; and reducing the incentives for lower paid, lower skilled workers to come here in the first place. We want to create the toughest system in the EU for dealing with abuse of free movement.
"We want EU jobseekers to have a job offer before they come here and to stop UK taxpayers having to support them if they don't ... EU jobseekers who don't pay in will no longer get anything out. And those who do come will no longer be able to stay if they can't find work.
"The British people need to know that changes to welfare to cut EU migration will be an absolute requirement in the renegotiation. I say to our European partners, we have real concerns. Our concerns are not outlandish or unreasonable. We deserve to be heard, and we must be heard.
"Here is an issue which matters to the British people, and to our future in the European Union. The British people will not understand - frankly I will not understand - if a sensible way through cannot be found, which will help settle this country's place in the EU once and for all.
"And to the British people I say this. If you elect me as Prime Minister in May, I will negotiate to reform the European Union, and Britain's relationship with it. This issue of free movement will be a key part of that negotiation.
"If I succeed, I will, as I have said, campaign to keep this country in a reformed EU. If our concerns fall on deaf ears and we cannot put our relationship with the EU on a better footing, then of course I rule nothing out. But I am confident that, with goodwill and understanding, we can and will succeed."