Shadow chancellor John McDonnell has defended the use of direct action tactics to protest about tax dodgers as he called for a "national debate" about the future of the economy.
The left-winger insisted that alongside parliamentary debates "we do need a bit of protest in this country" as he set out his plans for a "new economics" to redistribute wealth which will shift the burden of taxation away from low and middle earners.
Conservatives accused Mr McDonnell of planning "damaging tax rises on jobs, investment and earnings", after he said his plans would ensure the economy "serves everybody, not just the rich few".
But Mr McDonnell claimed the Tory warnings were a "fantasy" and joked they "must have been affected by the lunar eclipse".
The veteran campaigner defended the use of street protests and occupations as tactics to highlight problems with the way the economy worked.
Ahead of his first Labour Party conference speech since his appointment as shadow chancellor, he told ITV's Good Morning Britain: "I have called for direct action campaigns because that is the right of people to protest.
"I will give you one example, on tax justice. Years ago I was part of a tax justice campaign where we had meeting after meeting about how we make sure we tackle tax evasion, tax avoidance in this country.
"Along come a group of young people called UK Uncut and they took some direct action - they protested in the street, they occupied a couple of offices that were not paying their taxes.
"Eventually that meant that we started addressing the issue and even George Osborne then had to start addressing the issue.
"So sometimes, in addition to parliamentary debates, we do need a bit of protest in this country. That is exactly what I have been advocating.
"But it is purely non-violent protest."
He added: "If you upset people, people stop listening.
"But the whole point of today, actually, is to give people the opportunity to channel their ideas into a real national debate about the future of our economy.
"In that way, people don't need to protest, they simply need to join the Labour Party and become part of that discussion."
Mr McDonnell's speech comes as leader Jeremy Corbyn seeks to regain the initiative after activists denied him a vote at Labour's annual conference in Brighton on whether to keep the Trident nuclear deterrent.
Mr Corbyn wants to scrap the missiles, but unions Unite and the GMB insist they should be kept and delegates decided on Sunday that the subject should not even be debated in the four-day conference.
Meanwhile, The Times reported that a Unite official had proposed "stuffing" constituencies of centrist MPs who refused to serve under Mr Corbyn with supporters, in an apparent bid to force out moderates.
In a leaked email obtained by the paper, executive council member Tony Woodhouse reportedly said the union should "do a massive recruiting drive in the CLPs (constituency Labour parties) where MPs have said they wouldn't serve in his shadow cabinet".
But a Unite spokeswoman said: "As we have made consistently and regularly clear, Unite does not and will not support any moves to target MPs."
Mr McDonnell told ITV he wanted a "rational debate about our tax policies" and insisted that today was "the start of that debate, not the conclusion of it".
"We are going to set out our proposals this morning for opening up a national debate about where our economy is and where we need to grow it," he said.
"I have heard some of the rumours about massive tax increases - I think the Tory party must have been affected by the lunar eclipse last night, we have said nothing whatsoever. We are actually not making any major statements on tax today.
"What we are saying is we recognise there is a deficit and we are going to tackle that deficit. Yes, we are going to vote against some of the tax cuts for the rich that the Conservatives are introducing, our main thrust is around making sure that we tackle tax evasion, tax avoidance.
"But more importantly, we want to start growing the economy. So where they have got these fantasy figures about increases in taxes from, I have got no idea."
Mr McDonnell said he wanted to have access to public finance watchdog the Office for Budget Responsibility and the Bank of England to help Labour "model our proposals".