Theresa May has acknowledged the "uncertainty" created by Brexit after warnings by business leaders about the dangers of a sudden change in the trading relationship.

The Prime Minister said there "will certainly be challenges" but insisted that leaving the European Union would give the UK the flexibility to strike trade deals around the world.

She said the process would "take time" and stressed that the Government would not "rush ahead" - in an apparent rejection of calls from some Brexit campaigners for a swift break from Brussels.

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Brexit campaign chief Michael Gove has questioned experts on whether it would be possible for a "quickie divorce" and other Eurosceptics have suggested the process could take less than the two-year timescale set out under the Article 50 legal framework.

But at the CBI conference in central London, Mrs May told business leaders: "This is going to be a negotiation and it is going to take time."

Her appearance on the conference stage came after CBI president Paul Drechsler had urged the Prime Minister to give greater clarity about the Brexit plan.

He said firms were worried about "what happens on the day after Brexit", with some companies "inevitably considering a cliff-edge scenario - a sudden and overnight transformation in trading conditions".

The Prime Minister was urged to draw up plans for a "smooth transition" to give firms time to adjust.

Mrs May told the conference: "I know that leaving the European Union creates uncertainty for business.

"I know that some are unsure about the road ahead or what your future operating environment will look like.

"And there will certainly be challenges. A negotiation like the one on which we are about to embark cannot be done quickly or without give and take on both sides.

"But there are opportunities too. Opportunities to get out into the world and do new business with old allies and new partners.

"To use the freedoms that come from negotiating with partners directly to be flexible, to set our own rules and forge new and dynamic trading agreements that work for the whole UK."

She added: "I believe that if we approach the difficult negotiations to come in the right way and with the right spirit, we can strike a deal that is right for Britain and right for the rest of Europe too.

"The right approach is not to rush ahead without doing the groundwork, but to take the time to get our negotiating position clear before we proceed."

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She accepted that "businesses and others need some clarity" and promised to reveal details when she could - such as the promise to trigger Article 50 "before the end of March next year".

The negotiations would aim to ensure "the best possible deal for the UK for companies trading with and operating within the single European market", she said.