Prime Minister John Key says the case of an intellectually impaired New Zealand man who is reportedly being kept chained to a bed in Indonesia by his mother is very sad.

Mr Key, who is in Jakarta for a three-day trade mission, was speaking to reporters about the case of 26-year-old Simon Donaldson, who suffers from leukodystrophy and is being held by his mother in the city of Surabaya.

Her ex-husband, New Zealand businessman David Donaldson, and the couple's other children, have been battling to free Simon and have him brought to New Zealand where they say he will receive better care.

"The young man's obviously in need of help, the embassy here's been working jointly with the family and the authorities to try and provide that support and help,'' Mr Key said.


"He is a New Zealand citizen so he, technically and legally, is able to come back to New Zealand and get medical support, and I was with the ambassador when he raised the issue with the Indonesian Government on Sunday.''

"We are working on the issue but like all these consular issues, they're very complex. I don't think it's necessary to raise it with the President. Really he's at a different level,'' Mr Key said.

"What's important is those that can actually push this case through and give the support to this young man that he actually needs are at a different level and that was raised with those ministers on Sunday.''