The transport body will start collecting the anonymised data from its 260 WiFi-enabled stations in July to monitor how customers travel around using the tube.

TfL said it will use the findings to provide crowding data on its route planning website, share warnings about congestion at a ticket hall or platform level, and add the data to its API, which is used by apps such as Citymapper.

The move will expand TfL’s current data collection, which uses its ticketing system to track people’s entry and exit from stations. By using depersonalised WiFi data, it said it will gain more accurate insights on how passengers move through the network.

For example, a four-week pilot in 2016 found that there are at least 18 potential routes that passengers travelling between King’s Cross St Pancras and Waterloo could take – with around 40% of customers not taking the two most popular routes.

Lauren Sager Weinstein, chief data officer at TfL, said: "The benefits this new depersonalised dataset could unlock across our network – from providing customers with better alerts about overcrowding to helping station staff have a better understanding of the network in near-real time – are enormous. By better understanding overall patterns and flows, we can provide better information to our customers and help us plan and operate our transport network more effectively for all.

"We take our customers’ privacy extremely seriously and will not identify individuals from the WiFi data collected. Transparency, privacy and ethics need to be at the forefront of data work in society and we recognise the trust that our customers place in us, and safeguarding our customers’ data is absolutely fundamental."

TfL said it has worked with the Information Commissioner’s Office (ICO) to address privacy concerns, but the announcement has raised questions over whether the move is intrusive. While passengers’ movements will only be tracked if they are signed up to the network’s free WiFi, Eerke Boiten, professor of cyber security at De Montford University, told the New Statesman that TfL should have gone further. "Once people sign up or connect to the WiFi, they could give an option to sign out of being tracked."