More than a quarter of British Netflix subscribers allow their friends and family to use their accounts, with at least 17m homes estimated to be password sharing across the embattled streaming platform’s biggest markets in Europe.

Netflix announced plans to crack down on the practice as one of a number of strategic moves designed to stem investor panic after it had more than $60bn (£47bn) wiped off its market value last week when it reported its first loss of subscribers in a decade.

The world’s biggest streaming service, which expects its 221 million global subscriber base to shrink by millions more when it reports its next set of results covering April to June, has estimated that about 100m homes that pay for its service globally share their passwords with others.

In the UK at least 27% of Netflix’s estimated 14.9 million subscribers, more than 4m accounts, allow other households to use their accounts to watch shows from Bridgerton to Stranger Things for free, according to the research firm Digital i, which said the true figure is almost certainly higher.

“Our estimates came from analysing account activity, and we corroborated this with various other sources,” said Ali Vahdati, the Digital i chief executive. “That said, we still believe our results to slightly underestimate the [actual] incidence of password sharing.”

Its analysis revealed that account sharing is most prevalent among younger Netflix fans, with at least 29% of 18- to 24-year-old UK subscribers doing so. This compares with a more moderate 18% of 45- to 54-year-olds.

The research found that in Netflix’s five biggest European markets – the UK, Germany, Spain, France and Italy – a “minimum” of 17 million subscriber households share their passwords. The Spanish