Prime minister was forced to give up use of official plane for her Middle East tour as it was already in use by Prince Charles

Theresa May was forced to take a costly charter jet on her Middle East trade tour because the prime minister’s RAF Voyager plane was in use by Prince Charles, it has been revealed.

The former military plane was refitted last year for David Cameron – leading it to be nicknamed “Air Force Cam” – in an apparent cost-saving move, with No 10 saying it would be cheaper than chartering private planes.

The Ministry of Defence said at the time of the plane’s launch that it would save taxpayers £775,000 a year, and that it would also be used by the royal family.

Facebook Twitter Pinterest Theresa May arrives in Jordan on Monday. Photograph: Sam Lister/PA

The schedule clash meant the prime minister gave up the use of the plane for her trip to Jordan and Saudi Arabia, while Charles visits Italy, Romania and Austria.

The aircraft has 58 business seats for aides, business delegations and travelling journalists and is based at RAF Brize Norton. An RAF Voyager flight costs about £2,000 an hour, compared with an average private cost of £6,700, according to Downing Street sources.

Though it is not known how much the charter flight for the prime minister’s Middle East visit cost, Cameron’s January 2015 flight to Saudi Arabia after King Abdullah’s death cost £100,000.

A government spokesperson 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. The Prince of Wales is using it right now as he is representing the Queen on this tour he is on.

“Inevitably, there are clashes in scheduling. On a previous occasion, the PM used it and the Prince of Wales chartered an aircraft. This time, it is the other way round.”

The Labour MP Paul Flynn said: “This just shows that we are subjects, not citizens. It does seem to me to be outrageous. Of course the prime minister should have the first call on the plane – she is the elected ruler – ahead of some unspecified journeys by the heir to the throne.”