Boris Johnson has appealed to voters to ignore the "merchants of gloom" and choose a future for Britain outside the European Union.
The London mayor said that if people hold their nerve and vote for Brexit in the referendum on June 23, the UK could "prosper and thrive as never before".
Speaking at a Vote Leave campaign event in Dartford, Kent, he said: "I think the prospects are win-win for all of us.
"I think it is time to ignore the pessimists and the merchants of gloom and to do a new deal that would be good for Britain and good for Europe too.
"It is time to burst loose and of all those regulations and get out into a world that is changing and growing and becoming more exciting the whole time.
"If we hold our nerve and we are not timid and we are not cowed by the gloomadon-poppers on the Remain campaign and we vote for freedom and for the restoration of democracy, then I believe that this country will continue to grow and prosper and thrive as never before."
Mr Johnson said he was "very dubious" about the proposed deal with Turkey for visa-free travel within the Schengen zone.
"I am certainly very dubious on the other side of the coin about having a huge free travel zone," he said.
"I think that is one of the problems, that we need to take back control of our borders."
Mr Johnson also appeared to endorse Canada's arrangements with the EU as a potential model for Britain in the future.
Asked whether the UK would have to accept free movement of labour as part of a post-exit deal, he said: "I don't think that is necessary. I think we can strike a deal as the Canadians have done based on trade and getting rid of tariffs."
Aides pointed out that Canada had negotiated a package which meant around 98% of trade with the EU had zero tariffs, and it did not have to pay into the EU's budget or allow free movement.
Mr Johnson dismissed Mr Cameron's renegotiation as a "tragedy". But he again seemed to hint that a Brexit vote may not necessarily mean leaving - after he was forced to clarify recently that he did not think a second referendum was an option.
"The tragedy is we didn't get any real reform. Everybody knows it," Mr Johnson said.
"We didn't get any real change, the bureaucracy continues unabated. The only way to get the change we need is to say, 'Right that's it, we have had enough. This thing is 50 years old, it is going in the wrong direction, it is time for change, it is time for real reform'. The only way to get that is to vote leave."
He urged voters not to be "cowed by the gloomadon-poppers", saying the situation was "win win" and there were not "any substantial downsides" to leaving the EU.
Pressed on whether Brexit would mean another referendum on Scotland breaking away from the UK, the mayor said: "I don't think that is coming around again any time soon."
It would mean "nothing" if Scotland voted to stay in the EU while England voted to leave, because it was a UK-wide decision, he insisted.
Mr Johnson added: "I think the only thing we have to fear is fear itself."