Members of Leeds for Europe were joined by other Yorkshire pro-EU groups and anti-Brexit musician Peter Cook.
Amid a global pandemic and the day after Leeds United's promotion, Leeds for Europe chairman Richard Wilson - a Whites fan - said highlighting the upcoming "crisis" of Brexit was still vital.
He said: "We have a crisis with coronavirus and the last thing this country needs is a second crisis piling on top of it and to do that is just recklessness by our Government."
Pro-EU groups had been calling on the Government to extend the transition period - where the UK remains in both the EU customs union and single market - beyond December, but the Government chose not to do so.
It means the UK could be leaving on January 1 without a deal.
Mr Wilson said: "Now it is urgent that we get a good deal with the European Union to try to save our economy from further damage.
"While we've been distracted by the pandemic, understandably so, we've been drifting ever closer towards a real Brexit, which is at the end of this year when we leave the single market and the customs union and when things really start to change very suddenly.
"Like it or not we have to confront this situation with Brexit and we have to highlight the fact that the Government is leading us towards a cliff edge."
Mr Cook, who performed to around 50 demonstrators outside the Henry Moore Institute, said: "The lockdown has not caused any waning in opposition to Brexit. Groups throughout the country remain determined to highlight the harm Boris Johnson and his Government are doing to the country.
He started his 'Rage Against Brexit' tour outside the Islington home of Dominic Cummings, Boris Johnson's chief adviser.
Mr Cook, who has also performed in Skipton and York over the weekend, was due to perform today (Sunday) in Durham and Barnard Castle, which Mr Cummings visited at the height of lockdown, causing huge controversy.
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