Aides to Prince Charles have denied claims that he 'bumped' Theresa May off a plane used by the Prime Minister after he booked it for a tour of Europe.

May was unable to use the surplus RAF Voyager refuelling aircraft, which was refitted at a cost of £10 million last year for use by prime ministers, after reportedly discovering it has been reserved by the Prince of Wales for a nine-day visit to Italy, Romania and Austria.

Royal sources pointed out it was 'not her plane' and that the aircraft was free when the royal tour, which they said was at the request of the Government, was booked several months ago.

The clash meant that May arrived in the Middle East on Monday in a Boeing 757, featuring the logo of private charter firm Air Partner. She was in the region for three days to hold talks with King Abdullah of Jordan and King Salman of Saudi Arabia.

Prince Charles and Camilla used the plane for a four-day 'charm offensive' in Europe designed in part to soften up leaders in the run-up to Brexit negotiations.

The royals met Pope Francis at the Vatican in Rome and their schedule concludes in Vienna today, where they will visit the Musikverein concert hall.

Around 15 members of royal staff accompanied them on the trip. Foreign Office Minister Sir Alan Duncan also went with them on the plane around Italy.

Ambassadorial staffs, the police protection team and scores Ministry of Defence Staff also were on the plane, along with a press contingent who paid for their seats.

Palace officials dismissed reports that the plane is meant to be a dedicated plane for prime ministers. Former prime minister David Cameron claimed it would save the taxpayer £775,000 a year in private jet chartering fees.

The plane is reportedly earmarked for use by the Head of State (the Queen), the heir to the throne, when representing the Head of State and the Prime Minister respectively.

A Downing Street spokesperson played down the significance of Mrs May spending tens of thousands of pounds to hire another jet.

An official said: 'Ever since we first thought up the idea of the Voyager, it was always designed for use by the Queen and the Prime Minister or anyone attending international events representing the Queen or PM.

'The Prince of Wales is using it right now as he is representing the Queen on this tour he is on... Two visits at the same time means one aircraft will always have to be chartered.

'It makes no difference to the public purse whether Voyager is used by a member of the Royal Family or the Prime Minister.'

Labour MP Paul Flynn said: 'Of course the Prime Minister should have the first call on the plane – she is the elected ruler.'