Judge Baltasar Garzon's 300-page document must be approved by the Spanish cabinet before it can be presented to London.

In Britain, pressure is mounting on the general as he awaits an appeal hearing at before the House of Lords on Wednesday.

The human rights organisation Amnesty International has won permission to speak on behalf of alleged victims of the general.

"It is the first time Amnesty has intervened in a House of Lords case. It is very, very rare for this to happen," said Geoffrey Bindman, the lawyer representing those who say they and their families suffered under Gen Pinochet's 17-year rule.

Victims testify in parliament

At an unofficial hearing in parliament, anti-Pinochet activists testified to the human rights abuses allegedly committed by 82-year-old General Pinochet between 1973 and 1990.

Salvador Allende: Disappeared in 1973

Among them was Isabel Allende, the daughter of the former communist president Salvador Allende who was ousted in Pinochet's 1973 military coup and was never seen again.

Ms Allende, now a Socialist Party MP in Chile, told journalists about the events of 11 September 1973, when she last saw her father alive.

She said Chilean military forces led by Gen Pinochet bombed the presidential palace with her father inside.

"From the very first moment they had the intention to kill every single person they considered an enemy," she said, fighting back tears.

Ms Allende escaped the coup only with the help of the Mexican ambassador in Santiago.

She spent 15 years in exile in Mexico. Ms Allende said Gen Pinochet and his fellow coup leaders never showed compassion to their political opponents.

Isabelle Allende: Exile for 15 years

"They didn't have the humanitarian attitude that now they are asking for," she said.

Last week, the High Court ruled that General Pinochet had the right to diplomatic immunity because he was head of state at the time of the crimes alleged against him. But it said he had to stay in Britain pending the House of Lords appeal.

Wednesday's hearing is likely to last two days.

Amnesty will argue that Britain has a duty under a number of international conventions to prosecute crimes against humanity.

They will also state that General Pinochet, now a life senator, is not entitled to immunity because he is no longer head of state and the acts for which he claims immunity took place outside Britain.