Just Stop Oil -- a British environmental activist group focused on human-caused climate change -- took responsibility for the vandalism Thursday ... confirming they were specifically going after Taylor's private plane.

The org says protesters Jennifer Kowalski and Cole Macdonald entered the private airfield at Stansted airport around 5 AM ... and sprayed paint on PJs using rigged fire extinguishers.

The two gals who pulled this off were proud of the tag job ... posing in front of the vandalized planes and snapping selfies.

BTW, Just Stop Oil later confirmed they didn't end up actually hitting Taylor's jet -- they got 2 planes that didn't belong to her, but their intentions were clear ... evidenced in JSO's caption on the post for this, not to mention their own headline, which referenced Taylor lyrics.

Essex police confirmed they arrested the women ... noting the demonstrators were booked on suspicion of criminal damage and interference with the use or operation of national infrastructure.

Just Stop Oil says its end goal is for the British government to stop the extraction and burning of oil, gas and coal by 2030.

Macdonald added, “We’re living in two worlds: one where billionaires live in luxury, able to fly in private jets away from the others, where unlivable conditions are being imposed on countless millions."

Taylor officially reached billionaire status last fall ... with her "Eras" tour playing a major factor in her becoming a member of the three-comma club.

Yet, Taylor's consistently faced backlash for the frequent use of her private jet ... with her massive carbon footprint blasted online. It's been an ongoing criticism against her for years.

According to Just Stop Oil, private jet users are responsible for up to 14X more carbon emissions than a commercial flight.

Just Stop Oil also targeted UK landmark Stonehenge earlier this week. Similar to the jet situation, 2 protesters tagged Stonehenge with orange paint powder ... and they were also arrested.