Four anti-Brexit organisations are crowdfunding for a "war chest" designed to put pressure on the government for a second referendum.
Britain for Europe, European Movement UK, Scientists for EU, and Healthier IN the EU will use the cash to support rallies and lobbying, as well as paying for campaign materials for grassroots groups.
Rallies are planned at both the Labour and Conservative party conferences "to show the two main parties that we are European, and that Brexit should be, and can be, stopped".
The groups will also be holding a large lobby of parliament in October to engage directly with MPs.
The page, which launched this morning, has already raised more than £5,000 - but it is seeking £30,000.
Tax specialist and arch Remainer Jo Maugham is among those to have contributed so far.
"Brexit is not inevitable" the groups say. "When the final deal is put to Parliament, it must also be put to the British people to give them the option to reject it, and remain in the EU. Giving British people a real choice, based on fact, is the only democratic option for the UK Parliament."