A major report from Amnesty International released to coincide with this weekend’s Formula One grand prix has warned that human rights abuses in Bahrain continue “unabated” despite repeated assurances from the authorities that the situation is improving.

The Bahrain Grand Prix has become a prism through which human rights groups have sought to focus attention on the situation in the country after protests in the capital by pro-democracy campaigners in 2011 caused the race to be cancelled.

The Amnesty report details dozens of cases of detainees being beaten, deprived of sleep and adequate food, burned with cigarettes, sexually assaulted, subjected to electric shocks and burned with an iron. One was raped by having a plastic pipe inserted into his anus.

It said the report showed torture, arbitrary detentions and excessive use of force against peaceful activists and government critics remained widespread in Bahrain.

The organisation said the report showed the Bahraini authorities continued to abuse human rights despite repeatedly insisting they had exceeded the provisions set out in a report produced by the UN-backed Bahrain Independent Commission of Inquiry in 2011.

Earlier this year the UK’s foreign secretary Philip Hammond praised Bahrain as a country “travelling in the right direction” and other western countries have praised Bahrain’s progress.

But Amnesty concludes: “More than three years after Bahrain agreed at the highest level to accept and implement all the BICI recommendations, the steps introduced so far – while positive on a number of aspects – have been piecemeal and have had little impact in practice.”

Partly due to the unapologetic attitude of the Formula One chief, Bernie Ecclestone, who has tilted the calendar away from Europe and towards Asia and the Middle East, the sport has found itself at the centre of the debate over whether human rights should be a factor in staging major sporting events.

Two years ago Ecclestone said he thought Bahrain was “stupid” to host the grand prix because it gave demonstrators a platform to protest. He said it was not for him to judge how a county ran its own affairs. “We’re not here, or we don’t go anywhere, to judge how a country is run,” he said. “Human rights are that the people that live in a country abide by the laws of that country.”

Dissidents and exiled campaigners have warned that hosting the race increases instances of human rights abuses because authorities clamp down further on freedom of speech and assembly.

Amnesty’s report alleges the authorities have conducted a “chilling” crackdown on dissent, with activists and government critics rounded up and jailed, including some detained for posting comments on Twitter or – in one case – for reading a poem at a religious festival. Public demonstrations in Manama, the capital, have been banned for nearly two years.

Said Boumedouha, Amnesty International’s Middle East and North Africa deputy director, said: “As the world’s eyes fall on Bahrain during the grand prix this weekend, few will realise the international image the authorities have attempted to project of the country as a progressive reformist state committed to human rights masks a far more sinister truth.

“Four years on from the uprising, repression is widespread and rampant abuses by the security forces continue. The notion that Bahrain respects freedom of expression is pure fiction. Where is the freedom in a country where peaceful activists, dissidents and opposition leaders are repeatedly rounded up and arbitrarily arrested simply for tweeting their opinions, and reading a poem can get you thrown in jail?”

The Bahraini authorities have pointed to the economic benefits of hosting the grand prix, arguing it supports the employment of 4,000 locals and brings almost $300m into the economy.

This week, an organisation called Americans for Democracy on Human Rights in Bahrain said it had mediated an agreement with Formula One to implement a policy that analyses the human rights impact its presence might have on a host country. How that works in practice remains to be seen.

It said: “As a result of that process, Formula One Group has committed to taking a number of further steps to strengthen its processes in relation to human rights in accordance with the standards provided for by the guidelines. Formula One also takes this opportunity to reaffirm its commitment to respect internationally recognised human rights”.

During the mediation process Nabeel Rajab, a member of ADHRB’s advisory board and the president of the Bahrain Centre for Human Rights, was arrested.

The organisation said: “This arrest amounts to a signal that the government will broach no criticism or dissent before or during the race, which has previously attracted significant anti-government protest.”