The European Commission can no longer ignore mounting evidence of the gross human rights violations against migrants and refugees in Tunisia, say MEPs and activists.

The EU has given millions of pounds to Tunisia to reduce migration from north Africa into Europe in a deal that pledges “respect for human rights” and piqued the interest of the UK prime minister, Keir Starmer.

But a Guardian investigation this week reported on allegations of widespread abuses committed by EU-funded security forces in Tunisia, including sexual violence against vulnerable women.

There is now growing pressure on the commission to reveal how long it has been aware of reports of these violent practices, what it is doing to “remedy the situation” and whether more EU money will be sent to Tunisia.

“How is that reduction achieved? People are incarcerated, women are raped, and children are dumped and left to die in the desert; this is happening on a daily basis,” said David Yambio, spokesperson for the NGO Refugees in Libya.

“Each agreement made with the Tunisian and Libyan regime is a death sentence for migrants and refugees,” he added.

Catherine Woollard, director of the European Council on Refugees and Exiles, said: “These abuses are the horrifying yet entirely predictable violations that always result from these kinds of deals.

“Civil society organisations both in Tunisia and the EU are taking every possible step to defend the rights of those affected, including through direct assistance and support, litigation, monitoring and documenting abuses. Unfortunately, civil society is itself also being repressed.”

The Guardian investigation alleged national guard officers are colluding with smugglers to arrange migrant boat trips, as well as routinely robbing, beating and abandoning women and children in the desert without food or water.

German MEP Erik Marquardt said the EU needed to make an “honest assessment” of what was being done to tackle the criminal gangs involved in people-smuggling. “It’s not a conspiracy theory: it’s impossible for the smugglers to operate without the cooperation of the authorities.”

The families of detained Tunisian opposition politicians, who are already funding a case against the Tunisian authorities, are making a new submission to the international criminal court (ICC) next week demanding it open an investigation into crimes against humanity against sub-Saharan migrants.

The ICC, based in The Hague in the Netherlands, has the power to prosecute individuals and leaders for genocide, war crimes and crimes against humanity.

British barrister Rodney Dixon KC, who is leading the submission, said: “The new evidence shows that black African migrants are facing brutal and heartless treatment at the hands of the Tunisian authorities.

“The ICC has the jurisdiction to investigate these alleged crimes against humanity and should act with the full force of international law to protect those most vulnerable.”

A spokesperson for the commission said any allegations of wrongdoing by the Tunisian security forces should be investigated by the competent Tunisian authorities.

“The respect for human rights and human dignity of all migrants, refugees and asylum seekers are fundamental principles of migration management, in line with obligations under International Law. The EU expects its partners to fulfil these international obligations, including the right to non-refoulement. The commission remains engaged to improve the situation on the ground.”

The Tunisian authorities have rejected the Guardian’s allegations as “false and groundless”, saying that their security forces operate with “professionalism to uphold the rule of law on our territory, while fully observing international principles and standards”.

However, a spokesperson for the EU said it would shortly be contracting “independent monitoring experts to verify the respect for the ‘do no harm principle’ in the context of EU funded programmes”.