The European Union's chief negotiator has reminded Theresa May that the clock is ticking for Brexit negotiations ahead of her crucial make-or-break speech in Florence.

Michel Barnier, who is in Rome to meet the country's Prime Minister and attend a meeting of a parliamentary committee, said there was "only one year left to swiftly reach an agreement on the UK's orderly withdrawal".

“If we want an agreement, time is pressing. The Treaty on European Union provides for a two-year period to negotiate the withdrawal. Six months have passed since the notification letter of Theresa May, March 29, 2017. Six months will be required for ratification, before 29 March 2019," he told a joint meeting of the Italian parliament's the foreign affairs and European affairs comittees.

“We therefore have a useful year to find an agreement as soon as possible on the principles of an orderly withdrawal from the United Kingdom and to bring certainty where the Brexit creates uncertainty: for citizens, beneficiaries of European policies and border issues, in particular Ireland.

“[Also, to] define, as soon as the British Government so requests, the precise conditions of a short transition period; and, in parallel to the finalisation of this agreement, begin to define our future relationship. The sooner we will record real ‘sufficient progress’ on the conditions of the UK withdrawal, the sooner we can begin to discuss our future partnership.”

The chief negotiator, who is touring European capitals and speaking to officials and business leaders about Brexit while he is not negotiating with the UK, added that there would be no transition period – hoped for by some in government – if there was no deal. He said that this was a “legal” point.

But quoting notorious 16th century Italian politician Niccolò Machiavelli, he added: “Where there is a great will, there can be no great difficulty”.

It emerged on Thursday that nobody from the European Commission will be attending Theresa May speech in Florence tomorrow – despite the fact that Mr Barnier is already in Italy today.

Brexit: the deciders Show all 8 1 /8 Brexit: the deciders Brexit: the deciders European Union's chief Brexit negotiator, Michel Barnier Getty Brexit: the deciders French President Emmanuel Macron Getty Brexit: the deciders German Chancellor Angela Merkel Reuters Brexit: the deciders Commission President Jean-Claude Juncker EPA Brexit: the deciders The European Parliament's chief Brexit negotiator Guy Verhofstadt Getty Brexit: the deciders Britain's Prime Minister Theresa May Getty Images Brexit: the deciders Britain's Chancellor of the Exchequer, Philip Hammond PA Brexit: the deciders After the first and second appointed Brexit secretaries resigned (David Davis and Dominic Raab respectively), Stephen Barclay is currently heading up the position PA

The PM is expected to make an offer to the European Union, described by one Cabinet minister speaking to the BBC as "generous" as well as "open".