The only political party with official representation in government that supports and even calls for the removal of monarchy is the Green Party of England and Wales. A summary of their positions on the monarchy can be found in the party's 2005 General Election manifesto:
Elected House of Lords
The House of Lords will be reformed to become a fully elected body chosen by
A Constitutional Commission will be set up to draft a written constitution. The
Church of England should be disestablished and the monarchy should no longer
have formal legislative, executive or judicial roles.
The party, according to its wikipedia article, currently holds:
- 1 seat in the House of Commons
- 2 seats in the London Assembly
- 141 local government seats
Furthermore, a fairly well known political organization that campaigns for republicanism in the UK is the aptly named Republic pressure group. Republic is a member of the Alliance of European Republican Movements, a movement to abolish monarchy in European countries with members from seven of the extant European monarchies.
That said, none of the three major parties in the UK (the Conservative Party, the Labour Party and the Liberal Democrats) advocates for the abolition of monarchy. Also, in 2012 the monarchy enjoyed record support according to polls, with 69% of respondents saying that Britain would be worse off without the monarchy.