According to Which?, owners of devices including smart speakers and security cameras are being asked to provide swathes of data to manufacturers, which could compromise their privacy.

It could also result in them handing their personal information to social media and marketing firms, research from the consumer champion has found.

Concerningly, companies appear to hoover up far more data than is needed for the product to function including smart TVs that insist on knowing users’ viewing habits and a smart washing machine that requires people’s date of birth.

The research suggests that, despite consumers having already paid up to thousands of pounds for smart products, they are also having to ‘pay’ with their personal data.

Which? analysed the data collection practices of popular brands behind a range of smart devices. Experts looked at what information they require to set up an account, what data permissions their apps request and what activity marketing companies are tracking on people’s products.

When it came to smart cameras and doorbells, Which? found that every single one assessed used tracking services from Google, while Blink and Ring also connected to parent company Amazon.

Google Nest’s product demands full name, email, date of birth and gender. For smart washing machines, experts were surprised to find companies needed the date of birth of users – although this is optional on Beko machines, LG and Hoover will not allow use of the app without knowing when customers were born.

A third (33 percent) of the Which? members surveyed admitted to not reading any of the privacy policy when downloading an app, while two-thirds (67 percent) said that they merely skimmed it.

This is perhaps unsurprising given terms and conditions and privacy policies are usually incredibly long to read.

A Google Nest owner would need to work their way through more than 20,000 words to get to grips with them, which would take one hour and twenty minutes for someone who reads at 250 words per minute.

Under the General Data Protection Regulations (GDPR), companies must be transparent about the data they collect and how it is processed. The data collected must also be relevant and limited to what is necessary for the processing to take place.

However, the reasons for taking information are often too broad for consumers to appreciate, with companies claiming ‘legitimate interests’.

While it all should be listed in a privacy policy, the reality is that when consumers come to click ‘accept’, unless they closely analyse the fine print, they have little to no idea what will actually happen next with their data.

Rocio Concha, Which? Director of Policy and Advocacy, said: “Consumers have already paid for smart products, in some cases thousands of pounds, so it is excessive that they have to continue to ‘pay’ with their personal information.

“Firms should not collect more data than they need to provide the service that’s on offer, particularly if they are going to bury this important information in lengthy terms and conditions.

“The ICO should consider updating guidelines to better protect consumers from accidentally giving up huge swathes of their own data without realising.”

An Amazon spokesperson said: “We design our products to protect our customers’ privacy and security and to put our customers in control of their experience.

“We never sell their personal data, and we never stop working to keep their information safe. We use data responsibly to deliver what our customers expect: products that they love and are always getting better.

“We are thoughtful and transparent about the information needed to develop, provide, and improve the products and services that we offer our customers, allowing us to deliver a more personalized experience, and to analyse and improve the performance of our devices and services.”

A Google spokesperson said: “Google fully complies with applicable privacy laws and provides transparency to our users regarding the data we collect and how we use it.”

A Miele spokesperson said: “Miele is transparent with its customers about the use of data. The data is collected to optimise appliance usage and to offer customers additional features and functionalities.

Our digital services vary from country to country. By specifying the location, we ensure that we can provide customers with the relevant services,” Michael Prempert, Director PR Professional/Smart Home.

A Samsung spokesperson said: “We design our products with security and privacy top-of mind and our customers are given the option to view, download or delete any personal data that Samsung has stored across any product or app that requires a Samsung account. Customers can find more information about our privacy policies at www.samsung.com/uk/info/privacy”

Hoover/Haier and Bose declined to comment. Apple, Beko, Blink, Arlo, LG, Ring, Ezviz and Sony did not reply by Which?’s publication deadline.

Which? was unable to contact Eufy.