Prime Minister David Cameron’s hopes of being able to secure changes to the EU’s freedom of movement rules have taken a blow today after the outgoing European Commission President Jose Manuel Barroso told the BBC’s Andrew Marr show:

“Any kind of arbitrary cap seems to me to be not in conformity with European rules because for us it’s very important the principle of non-discrimination.”

“The freedom of movement is a very important principle in the internal market, the movement of goods, of capital, of services and of people.”

‘”In principle arbitrary caps seem to me in contradiction with European Union rules. That’s quite clear from my point of view.”

Mr Cameron said he would be looking to change policy on EU migration during campaigning in the Rochester and Strood by election, a contest the Conservatives are determined to win to ensure that UKIP does not secure another victory over the party and win a second seat in Westminster.

He pledged “one last go” on immigration and it was reported that he was going to demand an “emergency brake” on the numbers of EU migrants.

Plans are being drawn up to slash EU migration by imposing an annual cap on the number of national insurance numbers given to immigrants. The Tory proposals say that migrants would only get a national insurance number for a limited time in plans to deter migrants from moving to the UK permanently or for long periods of time.

Currently anyone from the EU can move to Britain and apply for a national insurance number.

For the proposals to not be in breach of EU law the same rules would have to be applied to UK citizens which would limit their ability to work and be part of the social security system and utterly undermine what the Prime Minister was planning to achieve.

Shadow immigration minister David Hanson told the Daily Mail:

“Why should anyone believe the Prime Minister when he has a record of making big promises on immigration and not delivering, when everyone knows he wants headlines for the Rochester and Strood by-election, and when the briefing from the Government keeps changing every couple of days?”

UKIP leader Nigel Farage was unusually on the same side as Mr Barroso:“Thank you Mr Barroso for speaking the truth [about immigration]”  he said.