Thousands of ‘dead’ satellites are floating in space and pose a ‘very big danger’ to humanity, the head of the European Space Agency (Esa) has warned.

Speaking at the agency’s ministerial council in Seville, Jan Worner said that of almost 4,500 satellites in orbit, only 1,500 are active.

Space scientists are concerned that defunct satellites could hit other satellites or the International Space Station (ISS), which would then cause more debris, setting off a catastrophic chain reaction that could wipe out telecommunications systems — a phenomenon known as Kessler Syndrome.