By Stephen Fidler and Jenny Gross

DAVOS, Switzerland -- British Prime Minister Theresa May said the U.K. would step up as a leading supporter of free trade, presenting in a speech here a strong defense of globalization and an implicit rebuke of policies suggested by U.S. President-elect Donald Trump.

"Forces that underpin the rules-based international system that is key to global security are somehow at risk of being undermined," she told the World Economic Forum in Davos.

Though she didn't mention Mr. Trump by name, she said the U.K. would forcefully back policies of free trade and international engagement that Mr. Trump has called into question. She described the global economic order as the crucial foundation for much of the global growth and prosperity since the middle of the 20th century.

Mrs. May said the U.K., even as it leaves the European Union, would continue to support the bloc's instinct to look to the wider world. She depicted Britain as the most racially diverse and multicultural country in Europe.

"I was surprised," said Harvard professor Ricardo Haussman, who was in the audience. "It couldn't have been more opposed to a Trump speech."

Britain "will step up to a new leadership role as the strongest and most forceful advocate for business, free markets and free trade anywhere in the world," Mrs. May said.

She said parties of the far left and far right, embracing the politics of division and despair, were seeking to exploit the sense that the economy wasn't working for them, meaning mainstream political parties needed to do more to look out for the less well-off.

Her commitment to Britain becoming a free-trade leader came two days after she announced the U.K. would be quitting its membership in Europe's single market, the world's largest trading bloc.

Instead, she said she would seek the "greatest possible access" to the single market through a free-trade agreement. On Thursday she added no further details regarding what she hoped to achieve in the U.K.'s future relationship with the bloc.

Some in the audience said the prime minister didn't resolve some contradictions in her position. Leaving the single market will likely reduce, at least in the short term, British access to its biggest market, thus diminishing the British economy's openness.

Mrs. May also insisted that big global corporations should pay their fair share of tax, despite suggestions from her government that if the U.K. doesn't get a good deal from the EU it would consider cutting corporate taxes to attract investments.

EU leaders have said theywould respond to her proposals once she formally launched negotiations with the EU over Brexit, expected by the end of March. EU officials have signaled that the U.K. won't have better trade access to the EU single market than it currently has as a member of the bloc. Britain voted 52% to 48% to leave the EU in a June referendum.

Mrs. May acknowledged that the negotiations with the EU would be challenging and that uncertainty lies ahead for the U.K.

"Britain must face up to a period of momentous change, it means we must go through a tough negotiation and forge a new role for ourselves in the world, it means accepting that the road ahead will be uncertain at times, " Mrs. May said.

Cecilia Malmström, EU commissioner for trade, who was in the audience, described it as a good speech. "She captured a lot of concerns, a responsible globalization that we are concerned about," she said.

In an interview in Davos before the speech, London Mayor Sadiq Khan said the city, Europe's financial capital, would need privileged access after Brexit to the single market and a continued ability to attract talent from abroad.

But he said that if business did have to leave London, it would likely also be a losing proposition for the rest of the EU.

"The evidence appears to be that businesses won't leave London to go to Paris, Madrid or Berlin; they will leave to go to Hong Kong, Singapore or New York," he said.

Also in Davos, German Finance Minister Wolfgang Schäuble said Germany's position wasn't to punish the U.K. in the negotiations.

He said the EU wants relations between the U.K. and Europe to be as close as possible but there will be a price tag for Britain's decision to leave the bloc. That is because Britain will lose the EU "passport" for financial services and the ability of firms based in London to clear transactions denominated in euros.

In aconciliatory comment, Mr. Schäuble said London "will remain an important place as a financial center" for Europe even after Britain-based banks lose the blanket right they now enjoy to conduct business across the EU.

--Andrea Thomas contributed to this article.

Write to Stephen Fidler at stephen.fidler@wsj.com and Jenny Gross at jenny.gross@wsj.com

(END) Dow Jones Newswires

January 19, 2017 12:07 ET (17:07 GMT)

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