Former Liverpool ace Didier Hamann says UEFA need to clarify the loan transfer laws.
Manchester City were hit with sanctions by UEFA in May for breaching Financial Fair Play (FFP) rules.
This month they recruited Lampard on loan until January from New York City FC - their American sister outfit, who the 36-year-old England international signed for after reaching the end of his contract with Chelsea earlier this summer.
And Arsenal manager Arsene Wenger subsequently questioned the arrangement, saying: "Is it a way to get around the fair play? I don't know."
Hamann, speaking in Manchester on Saturday at a McDonald's and Football Association Community Football Day, told Press Association Sport: "I think in the future that sort of thing could be an issue.
"I don't think it is an issue in this case, but in the future, if owners have a player somewhere else and then loan him back, it could be.
"Here it has happened with a player who is 36 and probably way past his best.
"If this was a player who was at his peak, then everyone would say 'hang on a minute - that's not right'.
"We have FFP and you should play by the rules and not try to bend it. This is certainly something that needs to be looked at.
"Everyone should be playing by the same rules - at the end of the day, that is why they brought it (FFP) in in the first place.
"UEFA has to be alert and aware because the clubs always try to get an advantage somewhere.
"I think the first step has been taken with FFP. At least something has been done in the last few years and we are headed in the right direction."
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