It will be "impossible" for Brexit talks to result in a deal that gives Britons more rights than others outside the EU, Italy's PM has told the BBC.

Matteo Renzi warned that leaving the EU would be a "very difficult process" - but the problems could be solved only after the UK began the exit procedure.

He said the Brexit vote had been "a bad decision" but had to be respected.

Meanwhile a German business leader said a so-called "hard" Brexit, rather than a "fudge", was the only option.Following the UK's vote to leave the EU in June's referendum, attention has focused on the government's likely demands in Brexit negotiations.

Mr Renzi said he had been shocked and saddened by the referendum result, but repeated Mrs May's vow that "Brexit is Brexit", saying democracy had to be respected.

Asked about whether there could be "flexibility" over EU rules on freedom of movement and access to the single-market, he said "I think this is a very interesting debate, because this debate will be a debate about the concept of rules in the EU."

But he said that debate could only begin once the UK had triggered article 50 - the official procedure for it to start leaving the EU - and he warned: "It will be impossible to give to British people more rights than other people outside the EU."

'Best alliance'

"The people of the UK decided the way for the future," Mr Renzi said. "Now the situation is that we can - and we have to - build the best alliance between the UK and the EU for the future because we will be the best friends for the next years.

"And at the same time I think this decision could push European leaders to invest in a new way for Europe."

Mr Renzi said Brexit discussions would be handled by the European Commission - not individual leaders or countries.

However, he added that he was ready to work with Mrs May "to support this very difficult process".

He said questions over the UK's departure from the EU need to be solved "as soon as possible".

Mr Renzi also blamed Brexit on David Cameron, saying the former UK PM had tried to solve internal problems within the Conservatives by calling the EU referendum.

The Italian prime minister, who has called his own referendum in Italy on whether to restructure the country's parliamentary system, said: "When David Cameron decided to use a referendum to solve some internal problems of the Conservative Party, this was the problem. We cannot use foreign affairs to solve internal problems."

Analysis

By Katya Adler, BBC Europe editor

Matteo Renzi was in a hurry.

He's always in a hurry. One of his nicknames is "frenzied Renzi" and this is a particularly busy week for him.

Here in Rome, Italian TV blasting out from bars and cafes features back-to-back rowdy studio debates about "Renzi's Referendum".

It's now set for 4 December - all part of the Italian Prime Minister's reformist drive to streamline and, he says, stabilise Italy's economic and political landscape.

Still, despite the hectic schedule, he managed to sit and engage with me in a debate, not just about his own political fortunes but about Brexit and the chance he believes it offers to reboot the troubled European Union.

Markus Kerber, the head of the influential BDI which represents German industry, said the UK would not be able to secure access to the EU single market without accepting the freedom of movement in its Brexit negotiations.

He told BBC Radio 4's Today programme: "We have a rough idea of what the British government wants to see.

"It wants to have relatively full access to the single market and yet limited on non existing freedom of movement of labour...

"That I think is impossible at the moment, so what we think the British government wants I can tell you straight away is not what the continental Europeans are willing or even able to give, then it will be relatively short negotiations."

Hard or soft Brexit?

• There is no strict definition of either, but they are used to refer to the closeness of the UK's relationship with the EU post-Brexit
• So at one extreme, "hard" Brexit could involve the UK refusing to compromise on issues like the free movement of people and losing access to the EU single market
• At the other end of the scale, a "soft" Brexit might follow a similar path to Norway, which is a member of the single market and has to accept the free movement of people as a result

Mr Kerber said it would be better to have a so-called "hard Brexit" which would not involve the UK compromising on freedom of movement "than to have a fudge in the middle".

Prime Minister Theresa May, who has said she will not formally trigger Brexit this year, is facing calls to clarify the government's demands from the negotiations.

Former education secretary Nicky Morgan, who campaigned for Remain in the referendum, told Today the PM could give a "broad outline" in her speech to next week's Tory conference and called for details to be provided "certainly in the next couple of months".

In other Brexit news, Mrs May has been urged to stamp out disagreement between the government ministers she has appointed to deal with Britain's exit from the EU.

The PM has put David Davis, Brexit Secretary, Liam Fox, International Trade Secretary, and Foreign Secretary Boris Johnson, in charge of the process.

However, the Institute for Government said her decision risks creating fragmentation and incoherence about who does what.

The think tank - which has close links to Whitehall - said the lack of clarity had already caused distractions which had wasted valuable time.

It called for another 500 officials to be hired to deal with Brexit - at a cost of £65m.