Prime Minister David Cameron will unveil what aides call a "far-reaching" immigration crackdown today on the eve of a European Union summit he will use to  start renegotiating Britain's ties with the bloc.

Speaking in London before flying to the EU's Eastern Partnership Summit in Latvia, Cameron will set out details of a new law to make illegal working a criminal offence.

The focus will be largely domestic, but the timing of his speech will be seen as a message to EU leaders about how important the issue is to him. Cameron is expected to remind them he wants the bloc to agree to allow Britain to sharply restrict EU migrants' access to its welfare system.

"A strong country isn't one that pulls up the drawbridge ... it is one that controls immigration," Cameron will say, according to advance extracts released by his office.

Cameron, who promised but failed to reduce net migration into Britain to less than 100,000 people a year during his last term, has pledged to give Britons an in-out EU membership referendum before the end of 2017.

One of his main aims before then is to reshape Britain's EU ties. He wants to force EU migrants to wait four years before accessing a range of welfare benefits, to win the power to deport jobless EU jobseekers after six months, and to generally make Britain a less financially attractive prospect for unemployed EU nationals.

The British leader says he wants to stay in a reformed EU, but has not ruled out recommending an exit if he doesn't get what he wants.

The summit agenda concerns the bloc's ties with six former Soviet republics, including Ukraine. But officials say Cameron will use the occasion to tentatively start his country's EU renegotiation in individual meetings with EU counterparts.

Since being re-elected, Cameron has already phoned several EU leaders to discuss the renegotiation, a process that will continue in regular diplomatic conversations and at other EU summits later this year.

If the renegotiation is completed early, Cameron has made clear he might hold the referendum before 2017. But he is under pressure from some of his own Eurosceptic MPs to take his time getting what they consider to be a meaningful settlement.

Some EU countries, such as France, have also ruled out the prospect of the bloc changing its founding treaties to suit Britain. British officials say Cameron remains convinced he will need such changes.