Astronomers have calculated that terrorists could use a series of nuclear explosions to steer an asteroid into the city of Telford, wiping out nearly half the UK. But Nasa denies even a 'madman' could manage it.

Large bodies of rock could be dislodged from their normal orbits by roughly 15 nuclear explosions, and aimed at an enemy country in a process scientists dub 'cosmic golf'.

In their simulations, Drs Holloway and Asher of Spaceguard UK landed an asteroid just 100 miles outside Telford.

"We have nothing against Telford, it happened to be near the middle and we had its position on file," said Dr Holloway. "But it demonstrates how easy it would be to achieve."

Worryingly, Holloway and Asher said it would be possible to keep Britain completely in the dark about the attack until it was too late.

"There are all sorts of ways of covering your tracks. Everyone would assume this was an act of God, when it was nothing of the sort," Dr Holloway told The Times newspaper.

"Cosmic golf is not just science fiction. It is beyond that," said Jonathan Tate, director of Spaceguard UK. "But the natural threat from asteroids colliding with Earth is far greater."

Others are more sceptical as to whether this could be carried out.

"The idea of redirecting an asteroid toward a target has been discussed many times," said David Morrison, a Nasa official. "But it is completely impractical, even if a madman wanted to try. We do not have the technology to aim an asteroid on impact on an impact trajectory."

Dr Holloway admitted this astronomical hype was actually designed to draw attention to the debate as to whether the Earth needs more funding to track rogue space bodies, rather than if a wannabe James Bond villain wished to pull his own Moonraker.

"There are positive benefits to this," agreed Spaceguard's Tate. "Such as the possibility of using a small asteroid to knock another [larger] one off course."