MANY of the arguments for Scotland staying in the UK are the same as Britain staying part of the EU, Jose Manuel Barroso, the outgoing President of the European Commission, has argued.

His comments were criticised by David Cameron, who insisted "the boss" on Europe was the British people not Brussels.

The Prime Minister's rebuke was in response to Mr Barroso's earlier remarks, denouncing the Tory leader's proposed cap on EU immigration as arbitrary and illegal. Mr Barroso warned him if Britain left the 28-member bloc then the UK would not even have "marginal relevance".

The EC President, speaking at the Chatham House foreign affairs think-tank in London, acknowledged there were "widespread concerns in the UK and elsewhere about abuse of free movement rights" and further changes could be made, although he stressed they would need the unanimous agreement of all member states.

Mr Barroso said it worried him "so few politicians on this side of the Channel are ready to tell the facts as they are; to acknowledge in today's world there are some things which we can only do effectively by acting together".

Claiming one could never win a debate from a defensive position, he referred to the Scottish independence referendum campaign, saying: "We saw in Scotland that you actually need to go out and make the positive case. In the same way, if you support continued membership of the EU you need to say what Europe stands for and why it is in the British interest to be part of it.

"In fact, even if I understand that emotionally the case for keeping the United Kingdom is different in nature, rationally many of the arguments used by the three main political parties in the Scottish debate are just as relevant for British membership of the EU."

But speaking later during a visit to the Ford factory in Dagenham, east London, Mr Cameron emphasised that what Britain needed was renegotiation of its EU membership, at whose heart would be addressing the issue of immigration, and then an in/out referendum for British voters to decide.

"I'm very clear about who the boss is, about who I answer to and it's the British people; they want this issue fixed, they are not being unreasonable about it and I will fix it," said Mr Cameron, who will attend a regular European Council meeting this week when the issue of reform, renegotiation and referendum is expected to be raised with Europe counterparts.

In light of the advance of Ukip - the Rochester by-election is on November 20 - the rhetoric of Mr Cameron and Tory colleagues on the EU has hardened in recent days.

Last week, the PM said he would have "one last go" at renegotiation; the implication being that if he failed, then he would recommend the UK withdraws from the 28-member organisation.

Elsewhere, Philip Hammond, the Foreign Secretary, said the Conservatives' attempt to enshrine the pledge to hold a referendum in law was "lighting a fire under the EU".

Deputy Prime Minister Nick Clegg, at his regular Whitehall press briefing, claimed the PM and his key lieutenants were "being pushed, day by day, week by week, by their right wing, because of their panic about Ukip, to the exit".

Shadow foreign secretary Douglas Alexander said: "The right road for Britain is change in Europe, not exit from Europe."

He added: "Just a few months ago, Conservative ministers were praising President Barroso's credibility when he spoke about Scotland and the EU, yet today they are trying to dismiss him because he has exposed that David Cameron's approach to Europe is weakening, not strengthening Britain's hand in Brussels."