LONDON (AFP) - British Prime Minister David Cameron vowed Tuesday to fight to the bitter end to stop Jean-Claude Juncker becoming the next head of the European Commission.

Mr Juncker is the candidate backed by the European People's Party, the largest group in the European Parliament, as well as by German Chancellor Angela Merkel.

But Mr Cameron strongly opposes his candidacy, saying he is a federalist who will not adopt the reforms that London says are needed to put the 28-member bloc back on track.

At a press conference in London with Chinese Premier Li Keqiang, Cameron said he was opposed to "having someone put on us by the EU parliament through a fairly strange set of elections." "I will continue to be opposed to that right until the end - there is no question of changing my view on that," he added.

Mr Cameron's words were the latest charge in his lengthy battle to stop Mr Juncker from taking the job.

Britain will hold an in-out referendum on its membership of the EU in 2017 if Mr Cameron's Conservatives stay in power at next year's general election.

The Conservative leader faces a challenge from a deeply eurosceptic group of lawmakers within his own party and from the anti-EU UK Independence Party, which secured the most votes in Britain's European Parliament vote in May.

European leaders are expected to hold talks on the European Commission leadership at a European Council meeting on June 26 and 27 in Brussels.