British Prime Minister David Cameron has secured allowance to a ban on in-work benefits for EU migrant workers, at a meeting with European Council President Donald Tusk.

The step will be enforced if London votes to stay in the EU. Other member states will also have to agree to the proposal.

If approved and introduced, it will affect Bulgarians and Romanians who arrive to the UK in the meantime, even if they work legally. The ban will apply to all other member states as well.

Under British legislation, tax relief and child and housing benefits could be provided to anyone working on a labor contract. Benefits are higher for workers earning the minimum salary, like most Eastern Europeans in the UK.

New rules setting out the mechanisms for member  states to block EU laws and certain business regulations could also be put in place. This is partly aimed at protecting non-euro states within the bloc.

A full statement by Tusk has been published on the European Council/Council of the European Union website. The negotiations between the two come at a time when the UK is planning to hold a EU in/out referendum by the end of 2017, with Cameron likely to schedule it for this summer.

Draft EU renegotiation document shows real progress in all four areas where UK needs change but there's more work to do.

— David Cameron (@David_Cameron) February 2, 2016

For Leave EU activists, however, the "emergency brake" is not considered to be big enough as a gain in Cameron's bargaining with the EU.

Another concession that is thought to have been secured involves the exemption of the UK from further political integration.

Cameron is due to visit Denmark and Poland later this week, as the beginning an attempt to convince member states' leaders to agree to the concessions.

Apart from a qualified majority, proof will also be needed on behalf of London that the country is affected by an influx of migrant workers from the EU.

In EU decisionmaking, a qualified majority requires 55% of member states (16 out of 28), representing at least 65% of the total population of the union, to vote in favor of a proposal to adopt it.