EU antitrust regulators aim to slap a hefty fine on Alphabet unit Google over its shopping service before the summer break in August, two people familiar with the matter said, setting the stage for two other cases involving the US company.

The European Commission's decision will come after a seven-year investigation into the world's most popular internet search engine was triggered by scores of complaints from both US and European rivals.

The EU competition authority accused Google in April 2015 of distorting internet search results to favour its shopping service, harming both rivals and consumers.

The Commission and Google declined to comment. The US company has in the past rejected the charges, saying that regulators ignored competition from online retailers Amazon and eBay.

Fines for companies found guilty of breaching EU antitrust rules can reach 10 per cent of their global turnover, which in Google's case could be about $9bn of its 2016 turnover.

Apart from the fine, the Commission will tell Google to stop its alleged anti-competitive practices but it is not clear what measures it will order the company to adopt to ensure that rivals get equal treatment in internet shopping results.

The regulator could set out general principles or specific instructions for Google to follow, said an observer.

The Commission's tough line is in sharp contrast with the US Federal Trade Commission which settled its own web search case with the company in 2013 by requiring Google to stop "scraping" reviews and other data from rival websites for its own products.