AstraZeneca misled patent regulators more than a decade ago in a bid to block competition to its ulcer drug Losec, an adviser to Europe's top court said on Tuesday, backing a €52.5 million EU antitrust fine for the British drugmaker.

The European Commission imposed the penalty on AstraZeneca in 2005, saying the company had given misleading information related to Losec, a bestseller at the time, to several national patent agencies in the European Union between 1993 and 2000.

The EU antitrust watchdog said such actions blocked or delayed the entry of cheaper generics to the market and also prevented parallel imports of the drug - when the same patented drug is brought in more cheaply from another EU country - proving that AstraZeneca had abused its dominant position in breach of EU rules.

AstraZeneca subsequently challenged the Commission's decision and fine at the General Court, Europe's second-highest, which upheld the regulator's decision in July 2010 but cut the fine to €52.5 million from 60 million. The company then appealed to the EU Court of Justice (ECJ) in Luxembourg.

ECJ Advocate General Jan Mazak said judges should dismiss the appeal.

"I consider that the General Court correctly found, on examination of the actual substance of the abuses in question, that those abuses were serious infringements," Mazak said in a non-binding opinion.

The ECJ, which typically follows the advocate-general's opinions in four out of five cases, will rule in the coming months.

The AstraZeneca case prompted EU antitrust enforcers to start an inquiry into the pharmaceutical sector in early 2008, which resulted in a critical report on "pay-for-delay" deals - when patented drug makers pay generics makers to hang fire - and subsequent raids on several drugmakers.

However, the Commission scrapped such investigations into AstraZeneca and Swiss peer Nycomed in March this year after failing to find evidence that the companies had undertaken such deals.

It also dropped a similar probe into GlaxoSmithKline after a U.S. rival Synthon withdrew its complaint.

U.S. regulators are also looking into such deals.