"I don't know if I am the most suitable person to be talking about signings by Real Madrid but these amounts seem excessive to me," Zapatero, a fan of Real's arch-rivals Barcelona, said in an interview with television broadcaster Cuatro.
"In principle, I don't like it."
New Real president Florentino Perez had spent around $94 million on Brazilian Kaka before his offer to Manchester United to buy Ronaldo and the club has said they want four or five more top players.
The huge transfer fees have shocked people in Spain, particularly with the country in deep recession, unemployment rising toward 20 percent and many soccer clubs saddled with huge debts.
Zapatero joined his economy minister, Elena Salgado, in urging the banks who are loaning Perez most of the money for his spending spree to extend credit to companies struggling to negotiate favourable loans.
ESSENTIALLY POWERLESS
But he said the government was essentially powerless to intervene in the workings of the free market.
"We cannot always complain in an economy with a free market when there is something we don't like, and there are a lot of things that I don't like," he told Cuatro.
"It would be bad for the government to step in and say to a bank, this credit yes and this credit no," he added. "It has to be the private sector that takes the risk."
Perez was quoted as saying on Wednesday that people who have called the club's spending immoral are ignorant and misguided.
Asked in an interview with newspaper Publico if he was annoyed when his bid for Ronaldo was labelled immoral, Perez told the paper: "No. I simply believe that it is a result of ignorance.
"This is a corporate project and some investments (in players) and those who see it differently are misguided. But time will prove us right and that's why I am relaxed," he added.
Perez has argued that the investment in Ronaldo, Kaka and others will more than pay for itself by generating new income from merchandising, the sale of audiovisual rights, advertising and marketing.
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