Richard Branson, the British billionaire founder of Virgin Galactic, on Monday hit out against "self-proclaimed experts" asserting an explosion was behind the crash of the company's spacecraft in the US last week.

Evidence showed there was "no explosion" behind the deadly crash last Friday of SpaceShipTwo, he told Sky News television.

"I've never seen such irresponsible innuendo and damaging innuendo," the tycoon said.

Branson also vowed to "push on" with Virgin's passenger travel space program once the reasons behind the accident, in which one test pilot died and another was injured, had been worked out and corrected.

"It's a grand program which has had a horrible setback," he said in a separate interview on NBC's "Today" show.

"But we owe it to him to continue," Branson said of the fallen pilot, Michael Alsbury, adding that the goal was "worth the risks."

Branson stressed on Sky News that the US National Transportation Safety Board (NTSB) investigating the crash had found that the spacecraft's fuel tanks and engine, retrieved from the Mojave Desert in California, had not broken apart.

"The fuel tanks and the engine were intact, showing there was no explosion, despite a lot of self-proclaimed experts saying that was the cause," he said.

Branson said sensationalist press reports about the crash had been "incredibly hurtful" adding that some of the journalists "should hang their heads in shame."

The NTSB has said it could take up to a year before it determines the cause of the crash, but noted that preliminary findings suggested a lock-unlock lever had been moved prematurely.

"If that ends up to be the case, that is something which is easy to fix, and we can make absolutely certain that it cannot be done again in the future," Branson told NBC.

The crash of SpaceShipTwo dealt a major blow to Branson's ambition to start ferrying wealthy customers to the edge of space, charging $250,000 (200,000 euros) per ticket.

But the serial entrepreneur made clear he was unbowed in his ambition.

"We must push on," he said.

He added though: "We will not fly members of the public unless we can fly myself and family members."

A rocket science safety expert on Sunday told AFP that Virgin Galactic had ignored multiple warnings about the spacecraft's motor and the fuel used since a 2007 incident in which three engineers were killed testing a rocket on the ground.

"I warned them... that the rocket motor was potentially dangerous," said Carolynne Campbell from the Netherlands-based International Association for the Advancement of Space.