British MEP Daniel Dalton, Catalan colleague Ramon Tremosa and Belgian MEP Sander Loones have asked the EU to find out if the transfer was supported by Spanish banks that had been bailed out by European Union tax-payers.
"If taxpayers' money was used to underwrite the Gareth Bale transfer deal then this is something the EU should investigate," Dalton was quoted as saying by British and Spanish newspapers.
"Real Madrid are the world's richest football club and if it has used a state-owned bank, owned by taxpayers, to guarantee ... record transfer fees then it is clearly something the EU should look to address to ensure there are no unfair competitive advantages given to football teams supported by taxpayer-funded financial institutions."
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Bale missed Real's 2-0 victory at AS Roma in the first leg of the Champions League last 16 on Wednesday because of injury.
The Wales winger has been out of action since damaging a calf muscle in a La Liga match against Sporting Gijon in January.
(Writing by Tony Jimenez in London; Editing by Peter Rutherford)
