Millions of UK PlayStation users have been victims of "excessive and unfair" download charges, a tribunal has heard.

A £2bn ($2.7bn) class-action brought against Sony by consumer campaigner Alex Neill claims the console maker prevented players from purchasing digital products outside of its own "closed eco-system".

Anyone who bought a digital PlayStation game or an in-game download over a period of about 10 years to February this year could be eligible for compensation if the case succeeds.

Defending its business model, Sony told London's Competition Appeal Tribunal that third-party stores posed a security risk and it also used software sales to subsidise sales of its consoles.

Opening the case for the claimants, Robert Palmer KC said Sony had "implemented a sustained strategy" to exclude competition over digital distribution of products "by monopolising their sale through the PlayStation store".

In order to publish "any content at all" for the PlayStation, he said, developers must sign a contract agreeing that it won't be distributed outside the official shop without Sony's consent.

The case claims the shop built into the PlayStation's operating system was designed to make players a "captive class".

Mr Palmer further claimed users faced restrictive licence conditions that prevented them from seeking to bypass those controls and obtain digital content from elsewhere.

"The result is that Sony can and does set the retail prices of all such content itself without facing any retail competition for digital content," he said.

"It allows it to obtain monopoly profits from digital distribution, setting retail prices at what it refers to as its target margin of an excessive and unfair 30% above the level of the digital wholesale prices."

The case claims Sony has unfairly profited from shifting consumer habits, with more players choosing to buy digital games over physical versions supplied on discs.

Its PlayStation 5 is available in three different models - only one of which comes with a Blu-Ray disc drive included, although it can be purchased separately.

Anyone who bought a digital PlayStation game or an in-game download over a period of about 10 years up to February this year could be eligible for compensation if the lawsuit is successful.

The claimants' legal team estimates 12.2 million users could be in line for £162 each, with the claim being brought on an "opt-out" basis, so eligible consumers will be automatically included.

Sony has told the court permitting use of third-party stores for downloads would introduce security and privacy risks.

The company has also said the commission it takes from digital sales is part of a strategy to cover the costs of its consoles, which it sells to players at a relatively low profit margin.

The case is the latest class-action lawsuit in the UK to target digital sales of software for various platforms.

A similar case, against PC games platform Steam, on behalf of 14 million users was allowed to proceed last month.

In October, the Competition Appeal Tribunal found that Apple abused a dominant position to charge developers commissions of as much as 30% on purchases from its App Store.

Apple is appealing against the decision.

The Sony tribunal is expected to last 10 weeks.

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