Some 12 per cent of UK and US users think nothing of piggybacking on unsecured Wi-Fi networks, according to research from Accenture.

The 18 to 34 group are the most likely offenders with almost a third admitting to 'borrowing' Wi-Fi access.

The survey, based on telephone interviews with 800 UK and US residents, showed that Americans were more likely to indulge in Wi-Fi piggy-backing.

One in seven US respondents admitted to the offence, compared to one in 11 in the UK.

The study also found that nearly half of respondents repeat their passwords online, while only one in four have ever encrypted a file on their PCs.

According to the researchers the findings indicate that users are underestimating the growing threat from cyber-criminals, who can easily gain access to multiple accounts once they successfully break into one account.

UK users are less likely to write down their passwords than their US counterparts. Nearly half of US respondents admitted to scribbling down their password, a practice denied by 70 per cent of UK respondents.