Fifa, football's world governing body, has said it will monitor Qatar's treatment of migrant workers building the 2022 World Cup facilities closely, following revelations that labourers on the first stadium under construction have been earning as little as 45p an hour and working up to 30 days a month.

A Fifa spokesperson said it had "repeatedly urged the Qatari authorities to address any unacceptable conditions for migrant workers in the country" and that while Qatar's reforms of workers' welfare represent a significant step in the right direction it would monitoring implementation closely for "concrete actions in the months ahead".

"We are doing everything in our power to improve the welfare of migrant workers and to use the hosting of the 2022 Fifa World Cup as a catalyst for positive social change," the organisation said.

The pledge to scrutinise Qatar's committment to worker welfare from the Swiss-based body came as the wage rates paid to workers on the Al Wakrah stadium were attacked as "deplorable" and "tainting football" by a series of senior British politicians.

Payslips of workers labouring on the stadium in ferocious desert heat showed they earned as little as £4.90 a day.

Labour and Conservative figures criticised the salaries, which Nick Raynsford MP, Labour 's former construction minister, said were "dreadful".

He called on British firms operating in Qatar, especially those such as Zaha Hadid's architectural practice, to show Qatar how construction of such events should be carried out responsibly.

"Given the amount of money being spent on preparations for the World Cup in Qatar it is utterly deplorable that no one is taking responsibility for the gross exploitation of the workforce including shockingly low pay," he said. "It is simply not good enough for Fifa or international architects working on these projects to wash their hands and say it is not our problem."

Jim Murphy, the shadow international development secretary, said the revelations were "utterly devastating for Fifa and Qatar 2022".

"When abuse of workers was first unearthed, football authorities assured us there would be change," he said. "But now we learn that the workers building world cup stadia – labourers the authorities have shown off as best practice – work for as little as 45p an hour. The exploitation has now entered the World Cup venues; the abuse is tainting football. This has to stop before the World Cup is permanently tarnished."

Hugh Robertson, the former Conservative sports minister who oversaw England's failed bid for the 2018 World Cup in the same round that saw Qatar secure the 2022 tournament, said the low wages were "clearly completely wrong".

"It is grim, and if you are paying people 45p an hour it is absolutely right the spotlight of world opinion should be on you," he said. "The ray of hope is that they have said they are going to do something about it."

Qatar's World Cup organising committee has said: "There are challenges with calculation of overtime pay and hours and we are working with the contractor to rectify any non-compliance."