Nepalese workers building stadiums for the 2022 World Cup in Qatar have been denied leave to attend funerals or visit relatives following the earthquakes in the Himalayan country that have killed more than 8,000 people, its government has revealed.

The government in Kathmandu has also for the first time publicly criticised Fifa, world football’s governing body, and its commercial partners. It insists that they must put more pressure on Qatar to improve conditions for the 1.5 million migrants employed in the Gulf state as part of the World Cup construction boom.

About 400,000 of the workers on the project are from Nepal, with the rest mainly from India, Pakistan, Bangladesh and Sri Lanka.

Tek Bahadur Gurung, Nepal’s labour minister, said: “After the earthquake of 25 April, we requested all companies in Qatar to give their Nepalese workers special leave and pay for their air fare home. While workers in some sectors of the economy have been given this, those on World Cup construction sites are not being allowed to leave because of the pressure to complete projects on time.

“They have lost relatives and their homes and are enduring very difficult conditions in Qatar. This is adding to their suffering.”

Gurung said Nepal’s government had been attempting, without success, to contact Fifa and its sponsors to ask them to be more robust with Qatar. “Nothing will change for migrant workers until Fifa and its rich sponsors insist on it. These are the people who are bringing the World Cup to Qatar. But we are a small, poor country and these powerful organisations are not interested in listening to us.”

South Asian countries have been reluctant to speak out about the controversy over migrant workers for fear of alienating Qatar.

Nepal has high unemployment and its government estimates that some $4bn is sent home every year by expatriates, most of them working in the Gulf. This accounts for about 20% of the country’s gross domestic product, and is money that will play a crucial role in helping to rebuild the country following the two recent earthquakes.

Gurung said: “We want to work with the Qatari government and bodies like Fifa because our people need the jobs and Nepal needs the money more than ever. Things are very difficult for the Nepalese and other workers in Qatar, but we have to help them and cannot stay silent any longer.”

Informal talks have taken place between the labour ministers of Nepal, India, Pakistan, Sri Lanka and Bangladesh with a view to establishing a more coordinated approach to improving conditions for workers in Qatar.

Their plight has once again been in the headlines. Last week it was reported that a BBC crew had been arrested and detained for two days while filming a report on the conditions of south Asian workers in the Gulf state.

Amnesty International published a report on Thursday saying that Qatar had failed to deliver on a range of promises to improve conditions and introduce new legislation covering migrant workers. This included abolishing the kafala system – which ties workers to their employers for a set period, during which they cannot change jobs without permission.

Migrant workers also often have their passports confiscated, may go for several months without pay, and have limited insurance against accidents.

“Without prompt action, the pledges Qatar made last year are at serious risk of being dismissed as a mere PR stunt to ensure the Gulf state can cling on to the 2022 World Cup,” said the Amnesty report, which also raised the issue of Nepalese workers being denied leave to return home after the earthquake.

Qatar’s supreme committee for delivery and legacy, the body overseeing World Cup projects, said that more than 500 Nepalese workers on World Cup projects had been given leave to return temporarily.

Gurung said: “There are far more than 500 Nepalese working on different World Cup construction sites, I can assure you. We have even offered to pay the air fare home for all our people building stadiums and involved in other projects, where companies are not willing, but not even this has made a difference. Our embassy in Doha has been inundated with requests for help from World Cup workers who are not allowed to leave.”

The minister said he was due to visit Qatar next month to hold discussions with his counterpart and meet Nepalese workers so he could see for himself the conditions they faced.

Qatar’s labour minister, Abdullah bin Saleh al-Khulaifi, visited Kathmandu last month and promised to introduce a series of changes. He also revealed that his nation would need even more Nepalese workers as it strives to complete World Cup stadiums and infrastructure projects in time for 2022.