Dozens of wealthy investors are considering pulling out of Sir Richard Branson’s Virgin Galactic programme, in a move which could cost the entrepreneur millions, it has been claimed.

More than 30 people who signed up to be among the first space travellers are now said to be reconsidering whether they want to make the flight in the wake of the crash of SpaceShip Two in California’s Mojave desert.

Copilot Michael Alsbury, 39, died in the crash last Friday, while pilot Peter Siebold, 43, remains in hospital.

Peter Ulrich von May, an asset manager based in Switzerland, is one of those who has demanded a refund. “I want out. I subscribed seven years ago at 63, am still an active private pilot and in good health but who knows how long it will now take. I have already informed VG of my wish - no reply yet,” he told The Independent.

Another of those who may ask for their money back said some people are “die-hard Richard Branson supporters and they will go on it whatever”.

However, speaking under condition of anonymity, they revealed that a group of more than 30 others have been talking about asking for their money back.

“Before this tragic event happened I had been thinking of pulling my money anyhow because there had been various reports saying it doesn’t stand a chance of getting into space,” they added. “I am giving serious thought to pulling out.”

Igor Kutsenko, who runs an advertising agency in Moscow and plans to go into space with his parents, said: “We were all shocked and disappointed by the tragic news. We are in the project from very beginning. My parents are getting older and I’m only worried that their physical ability to participate in this obviously challenging adventure is deteriorating. But we stay firm in our desire to make this suborbital flight.”

In response to the claim that more than 30 customers are considering their position in the aftermath of the crash, a spokesperson for Virgin Galactic admitted a number of people have asked for their money back.

“We can confirm that less than three per cent of people have requested refunds,” the spokesman said.

Hours after last Friday’s crash, Virgin asked its "Future Astronauts" not to talk to the press: “We are aware that a few of you are receiving press enquiries about today’s accident or may do so in the coming days. We would greatly appreciate it if you do not comment.”

In pictures: Virgin Galactic space rocket crash Show all 9 1 /9 In pictures: Virgin Galactic space rocket crash In pictures: Virgin Galactic space rocket crash Virgin Galactic space rocket A three-image combination shows the Virgin Galactic SpaceShipTwo rocket separating from the carrier aircraft, left, before it exploded, right, during a test flight on 31 October 2014 AP Photo/Kenneth Brown In pictures: Virgin Galactic space rocket crash Virgin Galactic space rocket Sir Richard Branson, founder of Virgin Galactic, with a scale model of the Spaceship Two attached to the White Knight carrier aircraft in this January 2008 photograph STAN HONDA/AFP/Getty Images In pictures: Virgin Galactic space rocket crash Virgin Galactic space rocket The Virgin Galactic SpaceShipTwo rocket explodes in the air during a test flight AP In pictures: Virgin Galactic space rocket crash Virgin Galactic space rocket Wreckage from Virgin Galactic's SpaceShipTwo Reuters In pictures: Virgin Galactic space rocket crash galactic-debris-reuters.jpg A piece of debris after the crash of Virgin Galactic's SpaceShipTwo near Cantil, California REUTERS/Lucy Nicholson In pictures: Virgin Galactic space rocket crash Virgin Galactic space rocket The suborbital passenger spaceship being developed by Richard Branson's Virgin Galactic crashed during a test flight on Friday at the Mojave Air and Space Port in California Reuters In pictures: Virgin Galactic space rocket crash Virgin Galactic space rocket Police officers stand near wreckage from Virgin Galactic's SpaceShipTwo Reuters In pictures: Virgin Galactic space rocket crash Virgin Galactic space rocket The wreckage of what is believed to be SpaceShipTwo in Southern California's Mojave Desert AP In pictures: Virgin Galactic space rocket crash Virgin Galactic space rocket A rescue crew carries a person on a stretcher to a waiting helicopter near the scene of a crash of the SpaceShipTwo in Southern California's Mojave Desert AP

Owned by Sir Richard’s Virgin Group and Aabar Investments PJS of Abu Dhabi, Virgin Galactic aims to fly people more than 62 miles (100km) above Earth.

More than 700 people, including Hollywood stars Angelina Jolie, Brad Pitt, and Tom Hanks, have bought tickets, which cost £156,000 each.

Princess Beatrice, who had planned to go on one of the space flights, is one of those said to have changed her mind. “Beatrice was excited by the idea of space tourism, but there is no way she will be going on one of the flights, if they are ever allowed to take place,” a source close to Buckingham Palace said in the Daily Mail today.

Despite revelations that experts had previously warned Virgin Galactic of safety concerns with SpaceShip Two, Sir Richard remained defiant. “When you have any incidents you get a lot of self-proclaimed experts coming out, a lot of whom know nothing about what they talk about,” he told the BBC.

The billionaire tycoon, speaking to Sky News, had planned to make the first flight next year with his son Sam, but insisted that “once it’s thoroughly tested, and we can go to space - we will go to space.” He declared: “We will not fly members of the public unless we can fly myself and family members.”

An investigation by the US National Transportation Safety Board (NTSB) into the cause of the crash is continuing, and pilot error has not been ruled out. The crash may have been caused by the prototype spacecraft’s unique “feathered” tail section, which unfolded prematurely. Designed to slow the 60-foot craft for a safe descent, it deployed too early, said NTSB officials on Sunday.