An alleged member of Basque separatists ETA accused of trying to kill Spanish King Juan Carlos would not get a fair trial if extradited, a British court heard Thursday.

Eneko Gogeaskoetxea Arronategui is fighting extradition from Britain to Spain to stand trial over accusations he was part of a plot to kill the king during a 1997 visit to the Guggenheim Museum in Bilbao.

Gogeaskoetxea, who was arrested in the eastern English city of Cambridge in July, was with a group that was stopped by police as they filled window boxes in the museum's gardens with explosives, the court heard.

A police officer, Jose Maria Aguirre Larraona, was shot dead as the group fled, lawyer Julian Knowles, representing the Spanish authorities, told Westminister Magistrates' Court in London.

In all Gogeaskoetxea, 44, is accused of 15 terror offences. These include planting bombs at Madrid Barajas airport, a bull ring and outside a court house. The only fatality from the attacks was the police officer.

"The defendant... is accused of committing a number of extremely serious terrorist offences in support of ETA, including the murder of a police officer, attempting to kill the king of Spain as well as helping to carry out a number of explosions," said Knowles.

But defence lawyer Edward Fitzgerald argued that Gogeaskoetxea would be denied a fair trial if he was sent back to Spain.

The evidence linking Gogeaskoetxea to the crimes was the testimony of his cousin Kepa Arronategui, he said.

He was arrested at the scene of the foiled Guggenheim bomb plot and gave a statement while being held incommunicado, but he withdrew the statement when the detention was lifted claiming police forced it out of him, Fitzgerald said.

"To send him back to a trial on evidence from an alleged accomplice during incommunicado detention amounts to a flagrant denial of justice," said the lawyer.

Gogeaskoetxea, who worked in IT, lived in Cambridge for a number of years under a false identity. He was arrested on July 7 after a fellow Spaniard recognised him at a squash club.

ETA, which is blamed for 829 deaths during four decades of bombings and shootings aimed at securing an independent Basque homeland, announced in October it was ending its armed activity.