Former Philippine president Gloria Arroyo has won backing from a United Nations body for her bid to be set free. The 68-year-old, who is suffering from debilitating neck arthritis, has been under "hospital arrest" since 2011.

The UN working group on arbitrary detention found her continued detention "arbitrary" and "violates international law", Mrs Amal Clooney, a human rights lawyer and wife of Hollywood actor George Clooney, said in an e-mail to the former president.

The UN body said in a report that the criminal cases filed against Mrs Arroyo have been "politically motivated since she is detained as a result of the exercise of her right to take part in government and the conduct of public affairs" and for her "political opinion".

It urged the Philippine government to allow Mrs Arroyo to post bail and accord her "an enforceable right to compensation... for the deprivation of liberty which already occurred".

Mrs Arroyo is being held at the Veterans Memorial Medical Centre over allegations she stole 399 million pesos (S$12.2 million) from the state lottery firm when she was president from 2004 to 2010.

She has repeatedly asked the Sandiganbayan anti-graft court to allow her to post bail for health considerations. The court has rejected all her requests.

The UN report backs appeals filed by Mrs Arroyo asking the Supreme Court to overrule the Sandiganbayan and allow her to post bail.

But defending the government's position, Justice Minister Leila de Lima said: "While international law forms part of the law of the land under the doctrine of incorporation, what is in our laws will have to be followed."

Mrs Clooney, 37, has had a high- profile legal career defending the likes of WikiLeaks founder Julian Assange and former Ukrainian prime minister Yulia Tymoshenko. This week, she won UN backing to set free former Maldives president Mohamed Nasheed.