The Liberal Party in Britain, apparently.
Interesting. Who was more anti-EU, Gladstone or Rosebery?
Oh wait, I didn't know of another Liberal Party.
Not sure if you're just joking or not, but the UK Liberal Party was a splinter group from the old party who left in part because of the merger with the Social Democratic Party to form the Lib Dems but mostly because they opposed EU membership and the euro, while the Lib Dems support both (but keep quiet on the latter these days).
It has a small number of local government councillors scattered around the country, most concentrated in Liverpool.
https://en.wikipedia.org/wiki/Liberal_Party_(UK,_1989)
Well, I'm being perfectly serious in reference to the Liberal cadiver which still randomly appears at council elections. 
The old Liberals were quite pro Common Market, but there was always a small anti-EEC grouping. The SDP was much more inflexible in its support for the Community.
The new SDP is very eurosceptic, from their own website:
"Brexit was a victory for democracy and accountability over lobbyists and bureaucracy.
The Social Democratic Party has a very positive vision of Brexit and, for that vision to be realised, we must ensure that the powers returned to our elected representatives are used to benefit society as a whole, rather than merely elements of it. "
