Zahir Belounis, the French professional footballer trapped in Qatar under its controversial labour laws, has written an impassioned plea to the former 2022 World Cup ambassadors Zinedine Zidane and Pep Guardiola asking them to intervene on his behalf. The 33-year-old has not been allowed back to France since June 2012 because he has been embroiled in a legal dispute with his former club al-Jaish, who play in the Qatar Stars League, over two years' unpaid wages.

Under the kafala system that ties employees to their "sponsors", migrant workers cannot leave the Gulf state unless their employer agrees and Belounis has been left in limbo in Doha with his wife and two daughters. In the letter to Zidane and Guardiola, who were both active ambassadors for the Qatar 2022 World Cup bid, Belounis says he has been "living a nightmare" in recent months due to a system that is "slowly killing me". He warns that "hundreds if not thousands" of others are suffering the same way and appeals to them as "fathers and former footballers" to do all they can to help him escape Qatar.

"I know that you served as ambassadors for Qatar's 2022 World Cup bid," said Belounis in his open letter. "You did this with good intentions but the reality is that if Qatar does not scrap its 'exit visa' system, then there will be hundreds, maybe thousands, of people trapped here."

Belounis acknowledges the commitment of those trying to organise the World Cup, which is likely to be moved to the winter to avoid the unsafe summer heat, and says the Middle East deserves to host the tournament. But he adds: "I ask you to use your influence as football ambassadors to talk about what is happening to me and what is happening to many other young men here in Qatar."

The global players' union, Fifpro, has said that Belounis had been forced to sell most of his possessions and it would forward an emergency payment from its hardship fund. Belounis said: "People are being kept far from their countries because of the exit visa system. This system should not exist and we need people like you, who love sport and its [good] image, to make our voices heard."

The intervention of the French embassy has not been enough to persuade the club to grant Belounis an exit visa. He believed he would be allowed to return home last weekend after signing a document giving up his claim to the unpaid wages but he was then asked to sign another document, which he believed could lead to him being charged with defamation and the imposition of a travel ban. He refused, believing that could leave him confined to Qatar for as long as the case took to be heard, which could be years.

Belounis, who has met France's president, François Hollande, over his ordeal, began legal action against al‑Jaish in February last year, claiming that money due to him from a new contract signed in 2010 had not been paid.

Fifpro this week wrote to Sepp Blatter, who visited Qatar last weekend, urging the Fifa president to intervene. It said it remained "deeply concerned" about Belounis's "precarious situation".

But on Thursday Fifa said it could do nothing to help Belounis because he had lodged a legal claim in the Qatar courts rather than taking the "second option available" of referring the matter to its dispute resolution chamber. Despite saying: "Fifa fully respects basic human rights and also requests that its member associations and the hosts of its events respect them," it said it was "unable to intervene". Fifpro said it was aware of "many more players and coaches" who were in a similar position in Qatar.

Zidane, the former world footballer of the year who is now a coach at Real Madrid, is believed to have been paid almost £2m to be an ambassador for the Qatar World Cup bid and helped revive the campaign at a crucial time following a Fifa technical report that flagged up concerns about logistics and the searing summer heat.

Guardiola, the Bayern Munich manager, played in Qatar for two years towards the end of his career and is thought to have played a key role in deepening the ties between the country's investment arm and his former club Barcelona. The Catalan club ditched their long-standing policy of shunning a shirt sponsor in favour of a deal with the Qatar Foundation and then Qatar Air. The Qatar 2022 bid team spent millions on ambassadors who also included the former Holland midfielder Ronald de Boer as part of an unprecedented spending spree to secure the World Cup in December 2010.

James Masters, a CNN reporter who has helped publicise the plight of Belounis, said this week that the player was close to suicide over the situation he had found himself in. Human rights organisations have warned that the kafala system that has left Belounis trapped in Doha has also contributed to the suffering of migrant workers in the construction sector, with the International Trade Union Congress claiming that up to 4,000 could die before the World Cup kicks off in 2022.

In his letter, Belounis says: "I am not alone in this predicament. Many workers who are to build the stadiums for the 2022 World Cup risk finding themselves in the same situation as me."

Many migrant workers are forced to sign away their claim to unpaid wages before being allowed to leave the country. A Guardian investigation showing that dozens of immigrant Nepalese workers had died in recent months alone in conditions akin to "modern day slavery" forced Blatter to address the issue last month.

But after last weekend meeting with the Emir of Qatar and the World Cup 2022 Supreme Committee, which includes many senior government ministers, he declared that he was happy with the progress being made on the issue of workers' rights.

Belounis said he hoped that as former players and parents themselves, Zidane and Guardiola would empathise with his predicament. "Imagine what I am going through every day in a house that is half-empty – because when they promised me that they would give me my exit visa, I sold my furniture – and when I see the look in my daughters' eyes, I feel ashamed, I feel disgusted with myself for inflicting such conditions on them."

The Qatar Football Association has denied Belounis's claims, saying that it had helped him recover unpaid wages when he played for another club in the country but that he had never lodged a complaint about al-Jaish.