Brexit supporters and opponents rallied near Prime Minister Theresa May's Downing Street office on Wednesday as her cabinet debated the draft divorce deal inside.
Pro-Brexit campaigners urged her to scrap the tentative agreement and make a clean break with European Union without paying a penny more into the EU budget.
"It sells out the country completely. We will be a vassal state of the EU," said Lucy Harris, founder the Leavers of London pro-Brexit group.
Around 100 demonstrators gathered opposite the Downing Street entrance gates, chanting "Theresa May, don't betray!" and "What do we want? Brexit. When do we want it? Now!".
They held painted placards reading "Ditch May's deal", "Let's take back control" and "Save Brexit".
"We're in a serious situation. It's a fork in the road. If this passes then we're in big trouble as an independent country," said Harris.
Niall McCrae, a lecturer in mental health at King's College London university, said the purported deal was a "stitch-up".
"How can they ask for our votes in future when they have told us our vote doesn't count?
"These votes have been annulled by our selfish political class."
'Nobody voted for that'
Britain voted by 52 per cent in favour of leaving the EU in a referendum in 2016 that exposed deep divisions in British society.
At another small rally near Downing Street, pro-EU demonstrators chanted "People's Vote", calling for a second Brexit referendum.
They accepted they had some common ground with the Brexiteers across the street: neither is happy with the way things are going.
"Brexit is a losing proposition all round. I think it's all madness. I'd say we're even more unhappy," said Nicky Gardner, 32, a student from London with two EU flags on a giant pole.
"Brexit has been failing all along and it's a matter of time before it hits the rocks."
Helen Campbell, 45, brought a toy unicorn with her to symbolise Brexit.
"It doesn't exist, it's a complete fantasy and can never be delivered," the freelance writer said.
"There is a lot of concern about what it actually means overall, and that we will be taking instructions from Brussels on a lot of our laws without any say in them, and nobody voted for that at all."
Pro-Brexit campaigners urged May to scrap the tentative agreement and make a clean break with European Union without paying a penny more into the EU budget.