By John Revill
INTERLAKEN, Switzerland (Reuters) - Britain's new prime minister must move quickly to "properly" leave the European Union, Brexit campaigner Boris Johnson said on Friday after Theresa May said she would step down.
Johnson, a Conservative lawmaker and former foreign minister, is favourite to replace May.
Speaking at a conference in Switzerland, Johnson said May had been "patient and stoical" in facing all the difficulties around the country's departure from the bloc.
She tried and failed three times to get a deeply divided British parliament to ratify her divorce deal.
"The job of our next leader in the UK, he or she, is to get out of the EU properly and put Brexit to bed," Johnson said.
"And to make sure we have an exciting, dynamic, but also socially compassionate conservatism that can see off Jeremy Corbyn and the Labour Party," he said, referring to the main opposition party.
He declined to give further details of his own leadership campaign, in which he will face rivals including Foreign Secretary Jeremy Hunt and probably former Brexit Secretary Dominic Raab, the ex-Leader of the House of Commons Andrea Leadsom and several others.
"I don't wish to elaborate on what I'm going to do and how we are going to do it, but believe me you will hear possibly more about that than you necessarily want to in the next few days," Johnson said.
The European Union has said repeatedly that it will not renegotiate the Withdrawal Agreement it sealed with Britain in November.
"A new leader will have the opportunity to do things differently and have the momentum of a new administration," Johnson said. The rise of populist movements in Europe could make officials in Brussels reconsider, he said.
The status of the border between British-ruled Northern Ireland and EU-member Ireland, a major stumbling block to May securing support for her divorce deal, could be resolved during an implementation phase of any trade deal, he said.
He said Britain could forge a "fantastic free trade relationship" with Europe after it quits the bloc but could also be a champion for global free trade.
Members of parliament could help by agreeing not to revoke Article 50, which triggered Britain's departure from the European Union after the 2016 referendum, he said.
"We will leave the EU on October 31, deal or no deal," Johnson said, adding a second referendum on EU membership would be a "very bad idea" and divisive.
(Reporting by John Revill, Editing by Michael Shields and Janet Lawrence)