Britain should be granted an opt-out from European Union laws to allow the Government to control migration, Boris Johnson has said.
EU leaders are "radically and dangerously misreading" David Cameron if they believe he wants Britain to remain tied to Brussels at any price, the London mayor said.
The Prime Minister is "much more eurosceptic" than some senior Tory figures and the UK must be offered reforms if it is to remain part of the 28-member bloc, he warned.
Mr Cameron has signalled he is ready to row back on key demands for welfare reforms in his renegotiation of Britain's relationship with the EU when he meets counterparts for talks at a summit in Brussels later this week.
He will tell leaders migration is a "major concern" in the UK but will insist that achieving a solution is more important than the way it is done.
Critics have likened Mr Cameron to a man "in a little dinghy" being towed along by the EU and many suggest he is not prepared to lead Britain out of the EU even if the results of his negotiation are minimal.
Mr Johnson said other leaders had given Britain the "bum's rush" by failing to agree to a ban on EU citizens from other countries claiming in-work benefits until they had been in the UK for four years.
Britain should be given a special settlement exempting it from some EU rules, like Denmark has over its laws blocking people from buying a house in the country unless they have lived there for five years, he said.
In his regular column for the Daily Telegraph, Mr Johnson wrote: "Waves of talent from overseas have helped to make our capital the most dynamic urban economy in Europe. But it should be up to us in this country to decide - as they do in America and Australia - whom to admit and when to admit them.
"Now our friends in Brussels have given us the bum's rush, and said that they won't agree to the four-year cooling off period that the PM has proposed. This would have meant that you can't come here and immediately clamp your jaws around the teat of the benefits system.
"I happen to think this idea would have been generally popular with European electorates, but never mind; they won't have it. So my question is: what will they agree to? We need to know.
"These people are radically and dangerously misreading the Prime Minister if they think he wants to stay in the EU at any price. The David Cameron I know is much more eurosceptic than some of his senior colleagues.
"We need to hear soon about ways in which the British Parliament can halt the tide of EU regulation, and ways in which we can regain some control of our borders.
"The PM's suggestion was modest, and sensible. It has been recklessly disregarded. This country could have a viable and exciting future outside the present EU arrangements. If we are going to stay, we need reform; and if the Danes can have their special circumstances recognised, so can Britain."
Mr Cameron is heading to the European Council summit on Thursday where, over dinner, he is expected to emphasise that "levels of migration from the EU to the UK are a major concern for the British people", but will signal he is open to other solutions.
The Prime Minister has previously conceded that no deal will be reached at the summit with the aim instead to seal a package of reforms in February.
Former environment secretary Owen Paterson said: "We were promised a major renegotiation, a total change with the relationship with our European neighbours."
Speaking to Murnaghan on Sky News, he added: "What actually is happening, he is like someone in a little dinghy, bumping along, being towed along by the enormous great Channel ferry.
"They are heading towards creating a new entity to make the eurozone work - a much more integrated political entity, almost like a new country.
"We can never go there - we will never be in the euro, we will never be in Schengen - and he is bumping around the back, towed along in the dinghy and this is all froth and bubble."