A spate of polls have put rejoining the EU back on the agenda – with a significant majority now backing re-entry into the bloc.
But the rally's organisers say "feet on the ground" are needed to make politicians take notice of the groundswell of support.
The National Rejoin March (NRM) will meet at 12 noon on Park Lane and march to a rally at parliament square.
They will hear from speakers including former Belgian prime minister Guy Verhofstadt and high-profile campaigner Gina Miller – who masterminded an anti-Brexit legal challenge.
"People are showing frustration because they feel they don't have a political voice. That's when people take to the streets: when they feel that they're not being heard," Ms Miller, who is now leader of the True and Fair Party, told The Independent:
Ms Miller, whose outfit is standing at the Mid Bedfordshire by election to replace Nadine Dorries, urged people to attend the rally.
"It's all very well having the polls move in favour of rejoining: you could have the polls every single week and they're all going in the same direction," she said.
"But when you see and hear people – the faces and voices – I don't think they can get away with pretending it's not an important issue to people. That's why the march is so important. It's a visual representation of what the polls are showing."
Earlier this year pollster YouGov's Brexit tracker found that 60 per cent of the public would vote to rejoin the EU.
Polls have repeatedly found signifiant support for rejoining the bloc.
Peter Corr, an ex-Army lorry driver who is co-founder and leader of the march, said: "We are urging all who want to rejoin to attend the second march and rally in London on Saturday 23 September.
"It’s time to turn polling support into feet on the ground. It’s no longer good enough to sit at home moaning about what’s happening to our country – let’s do something about it. We know the march and rally will add considerable momentum to the rejoin movement."