They were probably never destined to become best friends.

Britain’s Conservative prime minister has fallen out with the European employment commissioner Laszlo Andor – a left-wing Hungarian economist – over changes to Britain’s welfare rules designed to make it harder for migrants to claim certain benefits.

In an article in the Financial Times, Mr Cameron said he “shared concerns” about an influx of Romanians and Bulgarians, who will have the same right to work in the UK as other EU citizens from 1 January next year.

Mr Andor said the intervention could see Britain cast in the role of the EU’s “nasty country”.

He added: “The British public has not been given all the truth and the full truth about this subject. So we would need a more accurate presentation of the reality.” We’ll do our best.

Travellers queue to be processed by UK Border Agency immigration control officers at Heathrow airport's Terminal 5 in London

What’s new today?

EU nationals will not be able to claim out-of-work benefits for three months after arriving in Britain.

We FactChecked this issue many moons ago, and lawyers who work in the area told us it generally takes months anyway to pass the various hurdles necessary to start claiming out-of-work benefits.

It is possible to come to Britain as a jobseeker, but you have to pass a “habitual residence test” to get income-based jobseeker’s allowance. How long do you have to live here before the British authorities consider you a “habitual resident”?

There’s no statutory minimum time. In a test case in 2004 it was suggested that one to three months was appropriate.

Fixing three months as the minimum time could mean that some people are forced to live without benefits a few weeks longer. How many people will be affected? We don’t know.

Mr Cameron also announced that income-based jobseeker’s allowance will only be paid for six months, unless the claimant can show that he or she has “a genuine prospect of employment”.

That time limit is new, but it’s not as if people are allowed to claim jobseeker’s allowance forever without any checks now. Claimants constantly have to demonstrate that they are actively looking for work, or their benefits can be stopped.

There will be a new minimum earnings threshold for some benefits and EU jobseekers will no longer be able to claim housing benefit.

Beggars and rough sleepers will be deported. Many have been already since this pilot scheme was launched in 2010.

Only the first two changes will be ready by 1 January. The others are likely to take longer, according to the Prime Minister’s spokesman.

Will there be a crimewave?

Reports on the supposed dangers of mass migration from Romania have made much of Freedom of Information requests to the Met Police, which show relatively large numbers of arrests of Romanian nationals.

From 2008/09 to 2011/12 Romanians were the second most likely nationality to get arrested in London, after Poles (who are more numerous). There were 30,963 arrests of Romanians between July 2008 and June 2013.

That’s an unenviable position to be in, although the Romanian ambassador, Dr Ion Jinga, has made the fair points that a) these are  the numbers of arrests, not people – it could be that a small number of prolific criminals are being arrested over and over again and b) an arrest isn’t the same as a conviction.

Dr Jinga says 9,540 Romanian nationals were actually convicted of a crime in 2012, or 7.9 per cent of Romanians living in the UK, compared to an overall criminality rate of 9.16 per cent for all UK residents.

Do immigrants generally commit more crime than “natives”? The limited evidence we have suggests not. This UK Border Agency-commissioned report looked at the British Crime Survey from 2005 to 2009 and found that immigrants were about half as likely to be arrested or find themselves in court than native-born Brits.

Are EU migrants a drain on the state?

Quite the opposite, according to a growing body of evidence. Various studies show that most advanced economies benefit slightly from immigration, in that migrants pay more in taxes than they take out.

“EEA immigrants have made an overall positive fiscal contribution to the UK,” according to the Centre for Research and Analysis of Migration, largely because immigrants tend to be younger, healthier and less likely to claim benefits.

This paper from the National Institute for Economic and Social Research predicts that immigrants from Romania and Bulgaria will be similarly young, without families and looking for work.

By Patrick Worrall