BREXIT negotiator David Frost said Britain won’t budge on escaping EU rules.
He compared Britain to a guest “who had enough at the party and was trying to find a way to slip out”.
And he told the Brussels audience: “We were already in the hallway.”
Mr Frost insisted Britain is not "frightened" by warnings of extra friction in trade, saying the costs had been exaggerated and so too had the benefits of tariff-free trade.
He said Mr Johnson's Government "understands the trade-offs involved" and revealed they will be publishing a detailed blueprint for our future relationship next week.
In his forthright speech he warned Brussels they Brexit would make the UK more agile and its independence would allow the Government to correct bad decisions much easier and quicker. Mr Frost said: "The EU is going find this much, much more difficult."
He added: "Looking forward, we are going to have a huge advantage over the EU – the ability to set regulations for new sectors, the new ideas, and new conditions – quicker than the EU can, and based on sound science not fear of the future.
"I have no doubt that we will be able to encourage new investment and new ideas in this way – particularly given our plans to boost spend on scientific research, attract scientists and make Britain the best country in the world to do science. "
And hammering home the message that Mr Johnson is not bluffing when he says he will not be signing up to EU level playing-field rules, Mr Frost said: "Independence does not mean a limited degree of freedom in return for accepting some of the norms of the central power.
"It means – independence – just that. I recognise that some in Brussels might be uncomfortable with that – but the EU must, if it is to achieve what it wants in the world, find a way of relating to its neighbours as friends and genuinely sovereign equals."
Europe’s leaders have insisted we sign up to a “level playing field” on workers’ rights and state bailouts as the price for a trade deal.
Mr Frost said Boris Johnson’s stand “isn’t a simple negotiating position which might move under pressure”.
Warning the PM will instead walk away without a deal, he insisted: “We bring not some clever tactical positioning but the fundamentals of what it means to be an independent country.”
He added of being in the EU: “We never knew what we really wanted to achieve other than stop other countries do what other countries wanted to do.
“It’s so bizarre people told themselves Britain was winning the arguments or the EU is a British project. It’s clearly not.”
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Mr Frost said it is wrong to try to tie Britain to more than the EU asked of Canada or Japan in trade deals.
He said: “My experience is that EU has extreme difficulty in correcting wrong decisions.”
Nigel Farage said: “Great speech by David Frost in Brussels, the UK Government is sticking to the promises.”