A legal challenge to Australia's asylum seeker processing centre on Manus Island has been launched by Papua New Guinea's opposition.

Lawyers acting for PNG Opposition Leader Belden Namah filed a summons with the National Court on Friday.

Mr Namah said in a statement that he regretted taking the action against the PNG government but he believed the processing centre was unconstitutional.

''The ministers of the O'Neill-Dion government have now received a summons to appear and defend their conduct in the National Court,'' he said in a statement.

Mr Namah said the detainees on Manus were being held illegally in PNG.

''We will take this matter as far as necessary to ensure that the values of our nation's constitution are upheld,'' he said.

''This legal challenge also attempts to remedy the many abuses of PNG law and of ministerial powers which have given rise to the situation on Manus.''

Mr Namah said the opposition challenged the right of the government to force people seeking refugee status in Australia to enter PNG, where they were being held ''illegally and indefinitely under inhumane conditions''.

''We challenge the right of the government to make this arrangement with the government of a foreign nation, again in contravention of our constitution,'' he added.

The injunction seeks to have the current detainees released and to prevent the government from receiving or detaining any more asylum seekers from Australia.

''I am confident that our justice system will succeed in upholding this truth, where our government has so regrettably failed,'' Mr Namah said.

The National Court is yet to set a date to hear the challenge, the ABC reports.

AAP

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