Michael van Praag, the Dutch FA president who is one of three candidates challenging Sepp Blatter for the FIFA presidency, has been given the backing of the International Trade Union Confederation (ITUC).
The ITUC says Van Praag represents the best hope for migrant workers who are engaged on building projects for the 2022 World Cup in Qatar.
It comes as a meeting between Van Praag and the other two candidates, Prince Ali bin Al Hussein of Jordan and former Portugal international Luis Figo, ended without agreement that one of the trio would go forward alone to the May 29 election to take on Blatter.
The ITUC said Van Praag and the Dutch FA had taken the toughest line on "Qatar's notorious system of worker exploitation and the need for FIFA to act".
Sharan Burrow, ITUC general secretary, said: "FIFA can save itself from the catastrophe of a World Cup built on modern slavery in Qatar, by electing a candidate who will act decisively to support human rights.
"Prince Ali has also spoken strongly on the issue, but only one candidate, Michael van Praag, has put human rights in his official election manifesto.
"On that basis Mr Van Praag offers the best hope today that FIFA will finally put real pressure on Qatar to reform its medieval labour laws."
Blatter is the overwhelming favourite to be re-elected but some observers believe a single candidate would unite opposition to the 79-year-old rather than split the vote.
So far none of the trio has shown any inclination to withdraw - Figo would appear to be the most likely to do so but both Prince Ali and Van Praag have expressed determination to go all the way to the election.
The ITUC has also commissioned an Ipsos MORI opinion poll in the countries of the four FIFA candidates asking if respondents thought FIFA should reverse its award of the 2022 World Cup if Qatar's government did not amend its laws to help minimise accidents and the mortality rate of the construction workers.
Seven out of 10 respondents in Switzerland, home of Blatter, 64 per cent of those in Holland, and more than half in Portugal believed FIFA should reverse its decision under those circumstances.
In Jordan, three in 10 were undecided, 49 per cent said FIFA should not reverse its decision while 24 per cent thought it should.
Source: PA
