A nationwide series of "march for Europe rallies" will demand keeping close ties with the continent.
On the anniversary of the outbreak of the Second World War on Saturday, demonstrations in London, Edinburgh, Birmingham, Oxford, and Cambridge, will demand a pause in the Brexit process.
The marches are aimed at rallying support for keeping tight economic, cultural, and social ties with the rest of Europe.
The protesters want to halt the Government formally invoking article 50 of the Lisbon Treaty which triggers the two year deadline to withdrawal from the EU, and are backed by Labour's Chuka Umunna, co-leader of the Greens Caroline Lucas, and comedians Eddie Izzard and Josie Long.
The demonstrations are also calling for greater public consultation on every stage of the Brexit negotiations.
The rallies come after the Cabinet agreed immigration control would form a major part of Brexit negotiations, and ruled out a second referendum on the terms of withdrawal from the EU.