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 & 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 & 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 after this week.
He will tell leaders migration is a "major concern" in the UK yet will insist that achieving a solution is more significant than the way it is done.
Critics have likened Mr Cameron to a man "in a little dinghy" being towed along by the EU & 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 & Australia – whom to admit & when to admit them.
"Now our friends in Brussels have given us the bum's rush, & 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 & 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, yet never mind; they won't have it. So my question is: what will they agree to? We need to know.
"These people are radically & 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 shortly approximately ways in which the British Parliament can halt the tide of EU regulation, & ways in which we can regain some control of our borders.
"The PM's suggestion was modest, & sensible. It has been recklessly disregarded. This country could have a viable & thrilling future outside the present EU arrangements. If we are going to stay, we need reform; & 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", yet 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 alter 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 tremendous 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 – & he is bumping around the back, towed along in the dinghy & this is all froth & bubble."