This was done under the Investigatory Powers Act which was brought in in 2016. Saying that Labour weren't exactly against it at the time. Point being snooping isn't left or right - they all love it.
The Blairite wing of that party has always been extremely bad with this kind of thing (see Tony Blair's obsession with ID cards over the decades) so it's unsurprising they'd push something like this.
Oh wait....shit.