David Cameron insisted the EU needs to be run by people who understand the need for reform, as he was challenged over his opposition to Jean-Claude Juncker becoming the next head of the European Commission.
The Prime Minister said politicians in senior positions in Brussels had to understand the need for Europe to be more flexible and competitive.
His comments came as former prime minister Tony Blair set out an agenda for change in Europe but warned about the "dangerous" immigration policies of Eurosceptic parties such as Ukip.
Mr Cameron's entrenched opposition to the federalist Mr Juncker has led to accusations of "blackmail" by the former Luxembourg prime minister.
The Prime Minister is said to have warned German chancellor Angela Merkel at a summit last week that Britain could leave the EU if Mr Juncker is handed the job.
In response Mr Juncker told Germany's Bild am Sonntag: "Europe must not allow itself to be blackmailed."
Setting out his calls for European reform, Mr Cameron said freedom of movement was not an "unqualified right" and repeated his view that Brussels had become "too bossy".
Answering questions on the campaign trail in Newark he said: 'I've said very clearly when new countries join there should be much longer transitional controls, particularly when you've got countries with very different economic levels so we avoid the large migrations of the past.
"What I've said and what ... Conservative members of the Cabinet have said is that this right of free movement is not an unqualified right.
"The idea that we're members of the EU so you can apply for a job in another country and go work there that is a sensible thing but it's not an unqualified right. It shouldn't be a right to go somewhere and claim benefits automatically and we're changing those rules so that it can no longer happen so its not an unqualified right and we should be very clear about that as we seek to make sure that this migration system works for the UK and for hard-working people in the UK."
Asked why he was " trying to see off a former PM of Luxembourg nobody has ever heard of" Mr Cameron said: " We need a Europe that respects nation states, a Europe that gets the message from last week's elections that the EU has become too big, too bossy, too interfering, a very clear message that we need to make sure Europe is about competitiveness and about our countries winning in the global race against the Indias and Chinas.
"And my view is simple: we need people running these organisations - whether its the European Council, the European Commission or indeed any other part of Europe - that get that; that understand an open, flexible, competitive Europe that respects nation states and realises that the process of getting too big, too bossy, too interfering has gone too far and needs to be rolled back .
"And so that's what matters when it comes to these people, as you say, that no one has ever heard of. We need people that get it. That is my clear instruction on this and I look forward to the continued debate in Europe."
Mr Blair, who has been linked with the presidency of the European Council in the past, denied any interest in the Brussels post.
He insisted: "I'm not a candidate, don't get my position mixed up with this, that's not going to happen."
On the commission presidency he stated that the role should go to "the best person to do the job" but indicated that it should be a reformer.
He said: "There shouldn't be any predisposition towards one person or against any one person, we should just find the best person to do the job."
Proposing sweeping reforms he called for the European Council, made up of leaders from across the EU, to set out an agenda for change.
The officials at the European Commission and its new president would than be charged with implementing that programme, with the European Parliament debating and passing laws as necessary.
Mr Blair said the commission presidency was an important job and "if you define it in the way that I am defining it, in other words you want someone who is capable of driving through that big agenda, then that's the type of person you should go for".
The former Labour leader warned that it would be "complacent and dangerous" to ignore the rise of Eurosceptics, but Britain must lead reform rather than sever ties with Brussels.
In a speech at London Business School he said that leaving the EU would be "traducing" the country's national interest rather than standing up for Britain.
Mr Blair acknowledged there were justifiable concerns about immigration but condemned the way that foreigners had been blamed for taking British jobs.
Nigel Farage made tightening the immigration system a key part of Ukip's successful election campaign.
But Mr Blair, who called for the return of ID cards to address concerns on the issue, said it was "dangerous and wrong for leaders in British politics" to give people the idea "that what's holding them back is that somebody is coming in and taking that opportunity from them".
"The answer to the white, working-class unemployed youth in alienated communities in Britain is not to tell them their problems would be solved if there were fewer Polish people working in the UK," he said.
Instead they needed the skills to compete, he said. "It actually holds them back by giving them a grievance and not a chance."
Mr Blair added: "People can understand that immigration may be a good thing but they want some rules and order about it.
"I think you have got to distinguish between that and a desire to keep out people who are different, which I think is a regressive and a reactionary view you just have to take on."