The study showed that Google's market power has grown despite the EU's order for fair play

Three years ago, the European Commission imposed a fine of 2.4 billion euros (2.8 billion dollars) for this offence, Google subsequently invited competitors to bid for advertising at the top of the search page to direct traffic to their sites.

However, competitors said that the proposal was ineffective, and since then have called on the head of the EU antitrust agency Margrethe Westager to punish Google for failure to comply with its regulations.

The latest study conducted by consulting company Lademann & Associates covered the trade service Axel Springer Idealo, British company Kelkoo, French LeGuide and others in 21 European countries.

"This (Google's offer) has further strengthened Google's position in national markets to compare trade services and cemented its dominance in general search," said Thomas Hoppner, author of the study and consultant to several Google opponents.

"This is not because the Commission has introduced the wrong remedy. It's because Google's chosen compliance mechanism is not consistent with the remedy it has imposed," he said.

Hoppner urged the Commission to either force Google to come up with a more effective solution, or to warn the company for violating its order.

The Commission said it was monitoring the market to assess the effectiveness of Google's offer.

Google said the figures in the study ignore the facts and arguments of the commission in its decision.

"This tool has been working successfully for three years, generating billions of clicks for more than 600 trade service comparisons, and is subject to intensive monitoring," the spokeswoman said.