(Sharecast News) - The UK competition watchdog has accused Alphabet's Google of using its dominant position in digital advertising to hinder competition and favour its own services.

Releasing its provisional findings following an investigation, the Competition and Markets Authority said it believed Google had abused its dominant positions through the operation of both its publisher ad server and buying tools to restrict competition in the UK.

In addition, it found that Google "self-preferences" its own ad exchange, which harmed both competition and potentially thousands of British advertisers and publishers.

Juliette Enser, interim director of enforcement at the CMA, said: "We've provisionally found that Google is using its market power to hinder competition when it comes to the ads people see on websites.

"Many businesses are able to keep their digital content free or cheaper by using online advertising to generate revenue. Adverts on these websites and apps reach millions of people, assisting the buying and selling of goods and services.

"That's why it's so important that publishers and advertisers who enable this free content can benefit from effective competition and get a fair deal."

Google said the CMA's findings were based on "flawed interpretations" of the sector.

Dan Taylor, VP of global ads, told Reuters: "Our advertising technology helps websites and apps fund their content, and enable businesses of all sizes to effectively reach new customers.

"Google remains committed to creating value for our publisher and advertiser partners in this highly competitive sector. The core of this case rests on flawed interpretations of the ad tech sector."

Google's role in ad tech is also being investigated by the US Department of Justice and the European Commission. Last year, European regulators said Google may have to sell part of its ad tech business to allay concerns.

The US giant holds a key position in the sector, as it is able to collect data on users, thereby allowing advertisers to target their adverts.

It also sells advertising space as well as providing the technology that allows advertisers to find publishers to sell their space.

The CMA said it would now consider representations from Google before reaching a final decision.