The African Union is seeking to kill off the EU’s latest blueprint for stemming migration, claiming that it would breach international law by establishing “de facto detention centres” on African soil, trampling over the rights of those being held.

A “common African position paper” leaked to the Guardian reveals the determination of the 55-member state body, currently headed by Egypt, to dissuade any of its coastal states from cooperating with Brussels on the plan.

The EU set plans for “regional disembarkation platforms” in motion last summer to allow migrants found in European waters to have their asylum requests processed on African soil.

Brussels has a similar arrangement in place with Libya, where there are 800,000 migrants, 20,000 of whom are being held in government detention centres. The Libyan authorities have been accused of multiple and grave human rights abuses. A UN report recently stated that migrants in the country faced “unimaginable horrors”.

Some northern states, including Morocco, have already rejected the EU’s proposal over the new “platforms”, but there are concerns within the African Union (AU) that other member governments could be persuaded by the offer of development funds.

Italy’s far-right interior minister Matteo Salvini has called for the centres to be based around the Sahel region, in Niger, Chad, Mali and Sudan. An inaugural summit between the EU and the League of Arab States is being held in Sharm el-Sheikh in Egypt on Sunday and Monday, and migration is expected to be discussed.

“When the EU wants something, it usually gets it,” said a senior AU official. “African capitals worry that this plan will see the establishment of something like modern-day slave markets, with the ‘best’ Africans being allowed into Europe and the rest tossed back – and it is not far from the truth.”

They added: “The feelings are very, very raw about this. And it feels that this summit is about the EU trying to work on some countries to cooperate. Bilaterally, some countries will always look at the money.”

EU officials, in turn, have been coy about the purposes of the summit, insisting that it is merely an attempt to engage on issues of joint importance.

The leaked draft joint position of the AU notes that Brussels has yet to fully flesh out the concept of the “regional disembarkation platforms”. But it adds: “The establishment of disembarkation platforms on the African Continent for the processing of the asylum claims of Africans seeking international protection in Europe would contravene International Law, EU Law and the Legal instruments of the AU with regard to refugees and displaced persons.

“The setup of ‘disembarkation platforms’ would be tantamount to de facto ‘detention centres’ where the fundamental rights of African migrants will be violated and the principle of solitary among AU member states greatly undermined. The collection of biometric data of citizens of AU Members by international organisations violates the sovereignty of African Countries over their citizens.”

The AU also criticises Brussels for bypassing its structures and warns of wider repercussions. “The AU views the decision by the EU to support the concept of ‘regional disembarkation platforms’ in Africa and the ongoing bilateral consultation with AU member states, without the involvement of the AU and its relevant institutions, as undermining the significant progress achieved in the partnership frameworks and dialogues between our two unions,” the paper says.

Confidential legal advice commissioned by the European parliament also raises concerns about the legality of establishing processing centres on African soil for those found in European waters.

The paper, seen by the Guardian, warns that “migrants, after they have been rescued (or a fortiori after they have been brought back on to European Union territory), could not be sent to platforms outside of the European Union without being granted access to the EU asylum procedures and without being granted the possibility to wait for the complete examination of their request”.