Pro-Brexit - European Research Group

The long-established coalition of Brexit-minded Conservative MPs – though it publishes no list of members – led by Jacob Rees-Mogg, and one of Theresa May’s main obstacles in parliament.

Leave Means Leave

Headed by the businessman Richard Tice, and newly joined by Nigel Farage, this group seeks a Brexit completely outside any single market, customs union or EU oversight.

Change Britain

The successor group to the official leave campaign, it is headed by Labour MP Gisela Stuart, and says it wants to see the referendum result “respected and delivered in full”.

Stand Up 4 Brexit

A new group campaigning to sink May’s Chequers proposals, which claims the support of 20 Tory MPs, among them Priti Patel and Iain Duncan Smith.

Leave.EU

The unofficial leave campaign, financed by Arron Banks, which faces scrutiny about its tactics and funding. These days mainly a Twitter feed that mixes Brexit news with far-right-friendly messages about immigrants and Islam.

Soft Brexit/remain - Open Britain

Springing up in the wake of the referendum, this grouped MPs from various parties in pushing for a soft Brexit. It was supported by some Tories, such as Anna Soubry and Dominic Grieve, but they cut ties over a plan to oust hard Brexit-backing MPs.

Best for Britain

A later arrival, chaired by the former Labour minister Mark Malloch-Brown, this is more directly opposed to Brexit itself, and has received funding from the billionaire George Soros.

People's Vote

Part of Open Britain, this group calls for a referendum on the final Brexit deal.

European Movement

A long-established pro-EU group with sections across Europe, this has had a lower-profile role in the Brexit aftermath. Chaired by ex-Conservative cabinet minister Stephen Dorrell.

Our Future Our Choice

Set up by and seeking to represent young people, the group organises protests, and is probably best known for its eloquent spokesman Femi Oluwole.

For Our Future’s Sake

Going by the handy acronym of FFS, this is a student-based group seeking to block Brexit.

Scientists for the EU

A self-explanatorily named niche pressure group with a heavyweight set of scientific backers.