On the 12th anniversary of the arrival of the first prisoners at the US detention facility at Guantánamo Bay, the first commanding general of the base has said that it should be closed.

In a statement released by the advocacy organisation Human Rights First, Major General Michael Lehnert – who has spoken out on the issue before – said: “While there were compelling operational reasons to stand up Guantánamo prison early in the war [in Iraq and Afghanistan], we squandered international goodwill and lost opportunities by failing to adhere to the Geneva Conventions and to our own rule of law. Those decisions turned Guantánamo into a liability.”

Last May, in a major speech at the National Defense University, President Barack Obama detailed his continuing determination to close Guantánamo. Nonetheless, the base still holds 155 prisoners, of whom 76 have been cleared for release.

Lehnert continued: “The objective of terrorists is to change our behaviour and make us live in fear. By those standards our adversaries have been successful. We must reclaim our moral position.”

Guantánamo, which has been the subject of international protest since it opened, is sited on land controversially leased by the US from Cuba under a 1934 treaty.

“The Constitution does not stop at the waters’ edge,” Lehnert said. “We can defeat terrorism only if we do so in a manner that is consistent with American values. Guantánamo does not serve America’s interests. As long as it remains open, it will undermine America’s security and status as a land where human rights and the rule of law matter.”

Administrative attempts to reform Guantánamo continue. On Thursday, a government review panel that was established by an executive order from Obama cleared for release Mahmud Mujahid, a Yemeni prisoner who has been held January 2002. Mujahid, who had been accused but not charged of being a bodyguard for Osama bin Laden, is now deemed not to pose any danger to the US.

In December, after Congress passed a defence bill that cleared up transfer restrictions at the base, three Uighur detainees who had been held without charge for 12 years – and had been determined to pose no threat to the US – were transferred to Slovakia. The men could not be sent back to China, as their minority is persecuted there.

Such concerns are said to affect a number of prisoners remaining in Guantánamo, although December also saw two Saudi prisoners returned to their own country. One British resident, the Saudi citizen Shaker Aamer, remains in custody at Guantánamo.

In a statement accompanying Lehnert's comments, Dixon Osburn of Human Rights First said: “The United States has a legal obligation to find lawful dispositions for all law of war detainees when the war in Afghanistan ends this year.

“The administration must vastly accelerate the administrative review boards and obtain appropriate security assurances from host nations so that those detainees cleared for release can be sent home or resettled. The clock is ticking.”