Nepalese migrants laboring in Qatar continue to face miserable living conditions and exploitation, a researcher who was detained by the Gulf emirate has said.

Migrant laborers sleep up to 10 to a room and passports are still being confiscated, despite promised changes to the controversial kafala system which ties foreign workers to their sponsoring employers, Krishna Upadhyaya told VICE News.

Upadhyaya, 52, spent four days at the end of August visiting labor camps and speaking to Nepalese migrant workers in the Gulf emirate for Norwegian charity Global Network for Rights and Development.

He and his colleague Gundev Ghimire were prevented from flying home, however, after undercover police arrested him at the airport, detained him for 10 days, confiscated $11,500 worth of equipment including his laptop, cameras and footage, and charged him with possessing illegal documents.

He said: "We did what we wanted to do but we discovered after two days that we were being followed by plainclothes [police officers]. And then we tried to back up our work and save whatever we did."

The colleagues were held for 10 days in solitary confinement before they were finally released without charge.

However, they faced a further eight days' wait to secure permission to leave Qatar, before they were reunited with their families on Friday.

Upadhyaya, who grew up in Nepal but has British citizenship, said he hoped his arrest would help raise awareness of the working and living conditions of migrant laborers.

He said that accommodation was dirty and very basic, with kitchens that doubled as bedrooms, few showers, and cramped rooms.

He confirmed that the much-criticised kafala system, which Qatar has promised to abolish, was still in place. The workers typically earned 600 Riyal ($165) a month.

Qatar's gas wealth gives it the highest per capita income in the world, but it has faced repeated accusations of human rights abuses of its 1.4 million migrant workers.

The Gulf emirate plans to host the 2022 World Cup, and has embarked on a £123 billion infrastructure investment in preparation.

Qatar officials said they would scrap the kafala system in May; however, last month interior ministry officials said that reforms may not take place until next year.

Speaking from his home in North West London, Upadhyaya said that he was questioned for three days and held in a small, windowless cell

during his detention.

He said: "For three days they were asking why we were choosing Qatar, and not the other countries.

"The main thing they were asking was why Qatar, why are you portraying it as a negative picture. They were most concerned about that."

Upadhyaya confirmed that he was not tortured or mistreated, but said that he was concerned that he had no access to a lawyer, British diplomats or his family for a week after his arrest.

The Trade Union Congress's head of international relations, Owen Tudor, told VICE News: "The Qatari government's own figures show 40 construction workers dying every month, which means 160 workers are likely to have lost their lives since the unmet promise to reform kafala. The deadly delay continues a longstanding history of failing to match human rights promises with action.

"The Qatari government must prove it is serious about employment laws to better protect workers by welcoming foreign observers; not snatching them from the streets and throwing them in cells. Migrant workers must also be allowed to form free trade unions so that they can finally tell the truth about the conditions they face. "

Qatar's ministry of foreign affairs did not respond to requests for comment.