International pressure on Qatar to prevent exploitation of migrant workers in the buildup to the 2022 football World Cup escalated on Wednesday as victims' groups and the United Nations urged the game's governing body to act to halt a death toll that is already in the hundreds.

As the executive committee of Fifa convened in Zurich for two days of talks including a session on Qatar's preparations for the biggest sporting event ever to be held in the Middle East, the Uefa president, Michel Platini, said he was "much more concerned" with allegations over the treatment of migrant workers in the Gulf state than with discussions over whether to move the tournament to winter.

The British government also renewed pressure on Qatar, with the sports minister, Hugh Robertson, saying it should be "a precondition of the delivery of every major sports event that the very highest standards of health and safety are applied".

Unions have warned that labour conditions in the country could result in as many as 4,000 deaths before a ball is kicked. Representatives of the families of migrant workers already killed and injured on building sites in the Gulf state called on Fifa to hand the tournament to another country, unless the Doha leadership can quickly guarantee worker safety.

Ramesh Badal, a lawyer in Kathmandu who represents Nepalese workers victimised in Qatar, including those who have lost hands and legs in construction accidents, demanded that Fifa place a deadline on Qatar by which it must prevent deaths and labour abuses. He said if it fails, the right to host the World Cup should be withdrawn.

"If Fifa applies pressure on Qatar now, then they will definitely change," he said. "This is now in the hands of Fifa."

A construction site in Qatar, which has 1.2 million foreign workers and is spending £100bn on facilities and infrastructure before 2022. Photograph: Sean Gallup/Getty Images

Platini voted for Qatar to host the 2022 World Cup and his comments are one of the clearest signs yet that Qatar could be forced to act to safeguard more than a million migrant workers erecting nine new stadiums, motorways, metro systems, railways and several hundred thousand new hotel rooms. All 25 voting members of the Fifa executive committee who will convene to discuss the issue on Thursday and Friday were contacted to make them aware of the Guardian's findings. The treatment of construction workers in Qatar has been added to the agenda on Friday in the wake of the Guardian's reports, which found 44 Nepalese workers had died in Qatar between 4 June and 8 August this year. This week the Nepalese government revealed 70 nationals had died on building sites in Qatar since the beginning of 2012. Hundreds more are thought to have been injured in falls and accidents with machinery and vehicles.

Apart from Northern Ireland's Jim Boyce, who said he was "shocked" and "absolutely appalled" at the revelations about the treatment of migrant workers, none of the Fifa representatives contacted by the Guardian wanted to comment before the meeting.

The British sports minister, Robertson, told the Guardian: "I absolutely believe sports events should be spread around the world but one of the important consequences of doing that is that those countries that receive them should comply with the basic minimum standards of care."

The United Nations International Labour Organisation (ILO) called on Fifa to use the influence of the world's most popular sport to demand improvements in labour practices in Qatar.

"Fifa's power of persuasion is very big, bigger than the ILO, and they should use their influence," said Nada al-Nashif, the ILO director for the Arab states. "If they do that we can have a safe and happy lead-up to 2022. A lot hangs in the balance. We mustn't just make a few declarations and move on."

Platini told the Daily Telegraph: "I'm much more concerned about that [situation with migrant workers' safety] than the discussion about summer and winter. I prefer to discuss this at the Exco than in the press."

Qatar is spending in excess of £100bn on facilities and infrastructure before the 2022 tournament and is expected to bring in at least 500,000 more workers on top of the existing 1.2 million, including 340,000 from Nepal and more from India.

The International Trade Union Confederation wrote to the Fifa president, Sepp Blatter, on Wednesday to propose a series of joint ITUC/Fifa inspections of workplaces and living quarters in Qatar to monitor the treatment and rights of workers.

"The labour inspection system in Qatar has failed, and the government's announcement would simply add some inspectors into a system that doesn't work and will not make a difference," said Sharan Burrow, the ITUC general secretary. "Workers are not able to speak freely as, under the strict visa sponsorship system, employers retain their passports and they are not allowed to change jobs or leave the country without the employer's permission."

One Nepalese worker, Bhupendra Malla Thakuri, told the Guardian he was hospitalised for three months after a truck crushed his leg and he was paid nothing for all that time, was left without adequate medical support and was forced to take his employer to court to even afford a plane ticket home.

"When I was discharged … the company only paid me for the 20-odd days I had worked that month but nothing more," he said. "They didn't give me my salary. They didn't give me anything. It was a very critical situation. I was injured and my leg had become septic."

He added: "The failure to pay workers regularly is traumatising some of them."

Suresh Man Shrestha, Nepal's labour secretary, said the Kathmandu government had asked the Qatari authorities "to look into the situation of the migrant workers and to kindly stop any inhumane behaviour".

The ability of developing countries to negotiate with Qatar about worker welfare is affected by the fact that remittance money from migrant labour is an increasingly important part of their economies. Data published on Wednesday by the World Bank revealed 25% of Nepal's economy is now derived from remittances whose value to developing countries is set to reach $540bn by 2016 – a projected rise of 30% on current levels. India, which provides hundreds of thousands of workers to Qatar, currently earns more remittance money than any other country – $71bn a year.