David Cameron should not rush his negotiations with the EU because the "notoriously sclerotic" body makes scandal-hit Fifa look good, a Conservative MP has warned.

Jacob Rees-Mogg told IBTimes UK that the prime minister is an "extraordinarily strong" position to draw concessions from the 28-member block.

But the Eurosceptic backbencher argued that the historic referendum on the UK's membership of the EU should not be held until the dialogue between Westminster and Brussels has stopped.

"We should hold [the vote] when the negotiations have taken place and that will take time. But a negotiation that is hurried will not be one that achieves important changes because the EU is a notoriously sclerotic institution – it makes Fifa look [like] a model of how an international body should operate," Rees-Mogg said.

The comments come after Cameron travelled to Germany, France, Poland and the Netherlands last week to press his case for EU reform.

The Conservative leader seemed to make progress after the German chancellor, Angela Merkel, said she wanted to "find a solution".

But Cameron's plan, which includes proposals to limit benefits to EU migrants working in the UK, took a blow after the prime minister visited Warsaw.

Ewa Kopacz, the Polish premier, said the social security payments were a "fundamental right" and warned that the welfare changes could lead to discrimination against her compatriots.

Meanwhile, Jean-Claude Juncker claimed yesterday that the British electorate would not vote to leave the EU.

The European Commission president told German newspaper Süddeutsche Zeitung: "Brexit is not a question which arises, it's not desired by the British. Cameron wants to dock his country permanently to Europe."

But a "Brexit" is precisely the option Boris Johnson suggested Cameron should consider as the new Uxbridge and South Ruislip MP made his first speech to the House of Commons since his election.

"We now have a Tory government with a clear mandate to seek change and, therefore, a government in the most powerful position in our lifetimes to deliver reform and improvement in Europe," the Mayor of London said.

"If we don't get the deal that is either in the interests of this country or of Europe, then we should be prepared to strike out and forge an alternative future that could be just as glorious and just as prosperous with a free-trading arrangement."