US lawyer Kimberley Motley has said she was appalled at being denied access to her client, Anwar Ibrahim, by Deputy Prime Minister Ahmad Zahid Hamidi.

Motley said she had sought to meet Anwar at the hospital, in her capacity at the PKR de facto leader's international lawyer, but that her request was refused.

"I am appalled that Zahid and the Malaysian government have refused permission for this meeting.

"It is fundamental that a person is entitled to access to legal advisors of his choice whilst in prison.

"The rejection of my request to meet Anwar is in breach of international standards on access to justice, and paints Malaysia in a bad light," she said in a statement today.

Earlier today, Motley had also met with Pakatan Harapan chairperson Dr Mahathir Mohamad to obtain his support in advocating Anwar's release from prison.

Anwar is serving a five-year prison term at Sungai Buloh prison for sodomy, a charge he claims is politically motivated.

He was sent to prison in Feb 2015, but is expected to be released by the middle of next year, with his sentence cut short for good behaviour.

Anwar had been granted permission to stay at Hospital Kuala Lumpur pending recovery from surgery on his shoulder last month.