The UK has been branded “complicit” in a recent rise in the number of refugees and migrants dying in the Mediterranean, following the release of a damning human rights report.

Amnesty International said a spiralling death toll at sea and a surge in the number of people living in “squalid” detention centres in Libya was a “deadly consequence” of European Union policy.

More than 700 people died on the Central Mediterranean route from Africa to Europe between June and July, the report reveals, up from 597 over the same period last year. This came despite a drop in the number of people attempting to make the perilous journey.

The number of detainees in Libyan detention centres has also increased in recent months, from 4,400 in March, to more than 10,000 by the end of July, the charity claims.

According to the report, titled Between the Devil and the Deep Blue Sea, virtually all detainees were intercepted at sea and returned to Libya by the country’s coastguard, which is equipped, trained and supported by European governments.

Detainees are forced to live in “appalling” conditions and suffer torture, forced labour and even death, the report alleges.

Libyan Coast Guard puts refugees and rescuers in danger during rescue operation at sea

“Responsibility for the mounting death toll falls squarely on European governments who are more concerned with keeping people out than they are with saving lives,” said Matteo de Bellis, researcher on asylum and migration at Amnesty International.

“European governments are colluding with the Libyan authorities to contain refugees and migrants in Libya, despite the horrific abuses they face at the hands of the Libyan coastguard and in detention centres in Libya.”

The Independent reported last year how Britain had been supporting Libya’s coastguard, despite heavily documented evidence of refugee abuse and even instances of violent clashes with aid vessels.

Italy’s migration policy, implemented by its new right-wing government, is blamed by Amnesty for rendering search and rescue operations in the Mediterranean “unreliable, unpredictable, and punitive”.

Authorities have been denying entry to ships carrying migrants, forcing vulnerable people in need of urgent assistance – including pregnant women, torture survivors and unaccompanied children – to remain at sea for days on end, the report says.

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“In its callous refusal to allow refugees and migrants to disembark in its ports, Italy is using human lives as bargaining chips,” Mr De Bellis said. “Desperate people have been left stranded at sea with insufficient food, water and shelter.

“On top of this, the Italian and Maltese authorities have smeared, intimidated and criminalised the NGOs that try to save lives at sea, refused their boats permission to disembark and even impounded them.

“These serious incidents must be promptly and adequately investigated – they highlight the deadly consequences of Europe’s policies.”

Steve Valdez-Symonds, Amnesty UK’s refugee and migrant rights director, said: “The UK is as complicit as any other European government in the EU policy that now sustains a cycle of human rights abuse on a huge scale while humanitarian effort to save lives is deliberately undermined and obstructed.

“The truly dreadful outcomes for many thousands of children, women and men include exploitation, torture and far greater loss of life at sea.”