A year after Egypt's Islamist president Mohamed Morsi was ousted, the London-based human rights body Amnesty International says there has been a "catastrophic decline" in the country's human rights condition.

Amnesty said that a surge in arrests, detentions and harrowing incidents of torture and deaths in police custody signal the sharp deterioration of human rights in Egypt.

"On every level Egypt is failing in terms of human rights," said Hassiba Hadj Sahraoui, Deputy Director of the Middle East and North Africa Programme at Amnesty International.

"It is up to the new government led by President Abdel-Fattah al-Sisi to turn the tide by launching independent, impartial investigations into all allegations of human rights violations and send a strong message that flouting human rights will not be tolerated and will no longer go unpunished."

The organisation said that gathered evidence shows that torture – including electric shocks, rape, handcuffing detainees and suspending them from open doors – is routine in police stations and unofficial places of detention, particularly targeting Morsi's Muslim Brotherhood.

"Egypt’s notorious state security forces – currently known as National Security – are back and operating at full capacity, employing the same methods of torture and other ill-treatment used during the darkest hours of the Mubarak era," Sahraoui said.

Amnesty's statement stressed that thousands of Morsi supporters have been detained or faced trials on a variety of charges in the last year.

It also offered accounts from different interviewees who spoke of lengthy detention periods, sometimes without a charge, while being subjected to severe conditions, torture and sexual assault.

One interviewee said he was tortured to confess to charges of possessing explosives and belonging to the Brotherhood. Another said he was having difficulty breathing due to poor ventilation in his overcrowded police cell and was denied medical care. Others detailed accounts of sexual assault and rape in detention cells.

"If the Egyptian authorities wish to salvage any credibility, such horrendous practices must be stopped immediately," said the statement.

Commenting on the wide-spread allegations of torture in Egypt's prisons, a senior security aide to the interior minister said on Wednesday that the country's prisons are like hotels and that the claims of assault have nothing to do with reality or logic.

Amnesty's statement on Thursday also pointed to the hundreds of Morsi supporters who have been sentenced to death in recent months. In March, 529 were sentenced to death, to be followed the month after with a similar sentence for 683 others.

The sentences were later upheld for 220; others were given jail terms or acquitted.

"Egypt’s criminal justice system has suffered huge setbacks over the past year, with several politically motivated verdicts being issued," Sahraoui said.

Foreign ministry officials in Egypt have usually objected to local and international criticism, declaring it interference in Egypt's affairs.

Read the full Amnesty release here.