Britain is facing "a period of momentous change" following its decision to leave the European Union and will need to forge a new role in the world, Prime Minister Theresa May has told the World Economic Forum in Davos.

Ms May, who has said Britain wants a "bold and ambitious" trade agreement with the EU when it leaves the bloc, said Britain would step up to a new leadership role as a strong advocate for business, free markets and free trade after Brexit.

Discussions on future trade ties with New Zealand, Australia and India have already started, she said during a speech at the S

Ms May spoke of a truly global Britain, saying that Britain is and always will be open for business.

Multinational businesses must avoid short-term thinking and show leadership to help restore faith in globalisation among citizens who feel left behind by the pace of economic change, Ms May said.

She said businesses must put aside short-term considerations and invest in people and communities for the long term.

The British prime minister also said she is determined to ensure that centre-ground mainstream politics can provide answers for people.

Having famously rejected the notion at the Tory Party Conference of anyone being a citizen of the world, Ms May is entering the snowy citadel of those global chief executives, thinkers and campaigners who passionately celebrate that very ideal.

Many of those attending Davos this year will also be dismayed at the hard Brexit Ms May has chosen, and the disruption it may cause to the flow of goods and services back and forth from the outside world to the European single market.

Taoiseach Enda Kenny, also in Davos, will attend an informal gathering of heads of government and meet senior executives from a range of multinationals, including Facebook, AT&T, and IBM.

He will later deliver a speech to the heads of at least 45 global corporations at a dinner hosted by IDA Ireland.

Meanwhile, British finance minister Philip Hammond warned the EU that Britain would find other ways to remain competitive after Brexit if it did not strike a comprehensive trading deal with the bloc.

At the World Economic Forum, he stuck closely to the government's message that it wants to explore ways with the EU to ensure that decades of close ties are not broken - saying with goodwill, anything was possible.

But Mr Hammond, speaking to Reuters, said while the government did not want to leave the economic mainstream and trigger a race to the bottom on tax, the decision was "not entirely in our gift".

"We have to remain competitive. The best way to do that is to have a comprehensive trading relationship with the European Union, our closest neighbours."

"But if we can't achieve that then we will have to find other ways to maintain our competitiveness, because our first obligation of government is to make sure that our people are able to maintain their standard of living."

Mr Hammond later said that this was not a threat, but German Finance Minister Wolfgang Schaeuble said Britain should not try to gain competitive advantage by cutting corporate tax rates after the G20 leading economies agreed not to do so in 2015.

Recalling a pledge by Ms May to make Britain a global player post-Brexit, Mr Schaeuble said: "A truly global economy has to stick to what's been agreed globally."