MasterCard suffered a blow yesterday in a five-year fight against an EU ban on cross-border card fees, as an adviser to Europe’s top court backed regulators’ efforts to cut card costs.

The legal opinion follows a European Commission ruling that said MasterCard’s cross-border multilateral interchange fee, on retailers’ credit and debit card transactions, violated antitrust rules and had to be changed.

The crackdown is part of the Commission’s push to boost e-commerce in the 28-country EU and reduce costs for business, though MasterCard fears cutting the fees will discourage banks from issuing its cards.

“I propose that the court should dismiss the main appeal (by MasterCard) and the cross-appeals,” Advocate General Paolo Mengozzi at the EU Court of Justice said.

His recommendation signals how the final ruling may look.

The court, which will issue its ruling in the coming months, follows such advice in the majority of cases.

The opinion may also bolster proposed draft rules to cap charges on card payments that have yet to be approved by EU countries and the bloc’s parliament.

It is a setback to the world’s second-largest credit and debit-card company, which has said such interference would lead to higher costs for consumers and encourage the black economy.

MasterCard faces increasing competition from rival payment schemes such as eBay’s PayPal.