The US Federal Trade Commission said the company’s smart TV technology had captured data on what was being viewed on screen and transmitted it to the firm’s servers.

The data was sold to third parties, the FTC said.

Vizio has said the data sent could not be matched up to individuals.

It wrote: " [The firm] never paired viewing data with personally identifiable information such as name or contact information, and the Commission did not allege or contend otherwise.

"Instead, as the complaint notes, the practices challenged by the government related only to the use of viewing data in the ‘aggregate’ to create summary reports measuring viewing audiences or behaviours.”

'Second-by-second'

The FTC said the data collection began in February 2014 and affected around 11 million televisions.

"Vizio collected unique data from each household with a Vizio smart TV that included not only second-by-second viewing information, but also the household’s IP address, nearby access points, zip code, and other information,” the FTC said in a blog post explaining the settlement.

"They also shared that information with other companies."

It added: "This settlement stops Vizio’s unauthorised tracking, and makes clear that smart TV makers should get people’s consent before collecting and sharing television viewing information.”

As part of the settlement Vizio agreed to more prominently tell its customers how data is stored and collected, and to seek firmer, clearer consent beforehand. The company has been ordered to delete the data it collected.

Smart TVs - sets that have additional features such as on-demand viewing or video calling - have raised privacy concerns before. In 2015 it emerged Samsung’s models were transmitting potentially sensitive voice data without users’ knowledge.