The European Union's second-highest court has shot down an appeal by Google against a €2.4 billion fine imposed by Brussels for abusing its search engine dominance.

The ruling by the Luxembourg-based General Court confirmed the landmark decision taken by the European Commission in 2017.

The matter could be challenged again, however, if Google decides to turn to the EU's highest court, the European Court of Justice, for a final say.

The case centres on Google's shopping service and is one of three against the search engine giant currently moving through the EU's drawn-out appeals system.

At the time, the fine was the EU's biggest ever. But it was later exceeded by a €4.3bn fine against Google over Android, the company's smartphone operating system.

In its appeal, Google and its parent company Alphabet had argued the EU was "wrong on the law, the facts, and the economics" in the search engine case.

But the court said it dismissed "for the most part the action brought by the two companies, and upholds the fine imposed by the Commission".

It said that, by favouring its own Google Shopping service over rivals in its search result rankings and positioning, "Google departed from competition on the merits".

It rejected Google's argument that big online retailers had their own internet sites, saying that "those platforms are not on the same market" in which users go comparison shopping.

While Google was dealt a setback in the EU, the company fended off a separate legal case in Britain as the country's highest court blocked a class-action lawsuit accusing it of illegally tracking millions of iPhone users.

The Luxembourg ruling is a win for the EU's Margrethe Vestager, who burst onto the scene in Brussels by scrapping her predecessor's more conciliatory approach to the US tech titan.

Ms Vestager had lost in the same court in a different major case, against Apple and Ireland, in which her teams had ordered the iPhone maker to repay €13bn plus interest to the Irish taxpayer.

The EU has appealed that ruling.

The fine for Google came after seven years of investigation launched by complaints from other price-comparison services that saw traffic plummet against Google Shopping.

Experts believe that, if it is not overturned on later appeal, Google's similar forays into vacation rentals and job ads could be next in the EU commission's firing line.

Along with paying the fine, Google was told to remedy the problem identified by the EU case, even as the appeal moved forward.

The company tweaked its search display to give more prominence to rival shopping aggregators, as well as tourist and travel advice sites such as Tripadvisor and Yelp.

But many rivals are deeply dissatisfied with Google's fixes, believing they do nothing to guarantee fair competition in search results.

"What really matters... is stopping Google from repeating its behaviour in the future and protecting European consumers," said Richard Stables, from price-comparison site Kelkoo.

The commission, the EU's anti-trust enforcer, is currently preparing legislation expected for next year that would impose tough rules on Big Tech.

One of the laws, the Digital Markets Act, sets a clear list of Do's and Don'ts for internet "gatekeepers" that includes drastic limits on how Google, or other giants, can squeeze out rivals on their platforms.