LONDON (Reuters) - Nigel Farage, the Brexit campaigner who U.S. President-elect Donald Trump said would be great as Britain's envoy to Washington, taunted Prime Minister Theresa May with a mock ambassador's reception complete with chocolate and champagne.

May's government dismissed Trump's suggestion this week of "Ambassador Farage" saying there was no vacancy as Kim Darroch is currently serving as ambassador to Washington.

But at a party at London's Ritz hotel, Farage was cheered by his financial backers before offering guests pyramids of Ferrero Rocher chocolates, a joking reference to a long-running and much-lampooned 'ambassador's reception' TV advert in which the gold-foiled confection is cast as the delicacy of choice for diplomats.

Farage praised what he called "the political revolution" that had brought Brexit and then the election of Trump, whom Farage supported at a political rally before his victory.

"For those that are here who aren't particularly happy with what's happened in 2016, I've got some really bad news for you: It's going to get a bloody sight worse next year," Farage told guests from a staircase at the Ritz to laughs and cheers.

"I suspect there is another big seismic shock in British politics, perhaps going to come at the next election," Farage said after complaining that Britain was still ruled by "the career professional political class."

Farage told CNN he wanted a closer relationship between Britain and the United States and that he would like to act as a middle-man to improve relations.

He said he would be open to moving to the United States as a go-between if the British government wanted to follow Trump's suggestion: "It's up to the British government."

When asked by ITV television about Farage's ambassadorial ambitions, finance minister Philip Hammond said if he ever needed advice from the leader of the UK Independence Party, he had his telephone number.

"Tell him not to hold his breath," he added.

(Reporting by Guy Faulconbridge in London and Susan Heavey in Washington; editing by Stephen Addison)