By Thomas Escritt

AMSTERDAM (Reuters) - The lawyer for Libya's former spy chief Abdullah al-Senussi has demanded his surrender to the International Criminal Court (ICC) in The Hague, where he would not face the threat of the death penalty.

Senussi, notorious as right-hand man to slain Libyan leader Muammar Gaddafi, is wanted by the ICC on charges of ordering brutal reprisals during the uprising that toppled the Libyan strongman in 2011.

But in Libya, where he is associated with 1996 massacre of more than 1,200 prisoners in Tripoli's Abu Salim prison, authorities have been reluctant to surrender him, saying they can give him as fair a trial as the Hague-based court.

Senussi's lawyer, Ben Emmerson, rejected that assertion.

"For nine months," Emmerson told Reuters, "he has been kept in solitary confinement, isolated from the world. It is unheard of for a person accused of serious crimes - and who faces the death penalty - to be unable even to speak to a lawyer."

He was adding his voice to a chorus of human rights groups who have said Senussi and Gaddafi's son Saif al-Islam, who faces similar charges, should either be given access to a lawyer and a fair trial or be transferred to The Hague.

Echoing ICC judges, he said Libya was "completely unable" to conduct fair and impartial judicial proceedings.

Emmerson rejected suggestions by the ICC's prosecutor that Libya should be offered the chance to try Senussi and Gaddafi under the court's supervision if necessary.

"Mr Al-Senussi should be immediately surrendered to the ICC," Emmerson said. "His basic rights are being continuously violated in Libya. "

The court's cases in Libya have come to be seen as a test of its ability to make its writ run in places where cooperation is not guaranteed. Court officials attempting to interview Saif al-Islam were detained for a month last year, plunging the decade-old court into its biggest crisis.

Tripoli has challenged the ICC's right to try the duo under the principle that the international court only steps in where local legal systems are not up to the job.

It has pledged to abide by the ICC's final decision on the matter. But few expect Tripoli to surrender Senussi, after last year allegedly paying Mauritania $200 million to extradite him in defiance of the ICC's arrest warrant.

(Editing by Andrew Roche)