Manchester City and their sponsors manipulated contracts to circumvent Uefa’s Financial Fair Play regulations, according to Der Spiegel.
The German news magazine claims it has seen internal documents which show that City officials discussed how to wipe out a £9.9m shortfall in 2013.
Der Spiegel also reports that City owner Sheikh Mansour provided monetary supplements to existing deals with sponsors in Abu Dhabi, where he is part of the royal family, to invest more money into the club.
City say they will not be commenting on the claims, which come after initial allegations about the club and FFP were published by the magazine on Friday.
La Liga president Javier Tebas made a similar claim last year, with European football’s governing body Uefa responding by saying it was not investigating City, who have won the Premier League three times since Sheikh Mansour took over in 2008.
Uefa found City had breached FFP rules in 2014 and the two parties reached a settlement, with City paying a £49m fine – £32m of which was suspended – while their Champions League squad was reduced for 2014-15.
Der Spiegel calls the settlements “weak” and claims Uefa “wasn’t even entirely aware of the degree to which it had been deceived”.