Uncontrolled immigration into Britain has been too high under European Union rules, Boris Johnson has said.
The most high-profile figure in the Leave campaign said the current system had driven politicians to "dishonesty" because they were unable to control the numbers entering the country.
On his first day on the road with the Vote Leave battle bus, Mr Johnson said that he believed the UK should be able to turn away people arriving without a job offer as happened in the United States and Australia.
At the same time he said that outside the EU it would still be possible for governments to increase immigration if they could persuade voters it would "turbo charge" the economy.
Mr Johnson said that he was not proposing a particular ceiling for immigration - it would depend on the circumstances at the time.
"I haven't got a figure in my head and I wouldn't want to set a figure, but you need to look at each sector and you need to look at what the needs of the economy are, where it's useful," he said.
"What you certainly shouldn't do is promise to cut it to the tens of thousands and then it turn out that you've got hundreds of thousands."
His comments will be seen as a further swipe at David Cameron over his long-standing promise to reduce net migration to below 100,000-a-year - a target he has consistently failed to meet.
Mr Johnson went on: "It has been misleading. There is no question that it has been misleading. Politicians have been driven into this dishonesty about it by the EU's arrangements."
He said it was wrong that the country should have to let in so many people without popular consent.
"To add a city the size of Newcastle every year, we've seen nothing like it for 80 years or so. Let me put it this way, it's too high to do without consent. That is the issue," he said.
"It might be that a party or government or politicians could persuade people if they believed people that it was a good thing and it would turbo charge the economy and all the rest of it. What is not acceptable is to say there's nothing we can, that's just the way it is. That's not how other countries have it."
The "huge flows" of migrants were, he said, in part due to the "massive wage differentials" between the UK and parts of the EU.
"One of the things we're saying is that if you continue with the living wage and uncontrolled immigration you will get huge numbers," he said.
"I think when you have control, there should be ways of saying if you don't have the job offer, if you don't have the right qualifications, just as you can be turned away from the United States or Australia, you could be turned away from the United Kingdom. That would be totally reasonable."
Mr Johnson also indicated that he would be prepared to go head-to-head with Gordon Brown after the former prime minister challenged him to a referendum debate.
"I am the humble servant of the Vote Leave operation. If they point me I'll march. I'll do whatever is necessary. Let's see what they want to do. I'm up for anything," he said.