Teenage climate change activist Greta Thunberg has tweeted a photo of herself sitting on the floor of a busy German train as she returns to Sweden after an exhausting year travelling the world to lobby governments into taking action against global warming.

“Traveling on overcrowded trains through Germany. And I’m finally on my way home!” the protest icon wrote, including the shot of herself looking out of a carriage window surrounded by a heap of suitcases and rucksacks.

But in so doing, the 16-year-old inadvertently found herself drawn into Twitter hostilities with local rail operator Deutsche Bahn, which took umbrage at what it felt was implied criticism of its seating arrangements.

The company, under fire in recent years for delays, last-minute train cancellations and expensive ticket fares, initially responded to Thunberg’s tweet by wishing her a safe trip back to Stockholm and pointing out the ICE 74 train she was riding was 100 per cent electric, hoping to win her approval.

“We continue working hard on getting more trains, connections and seats,” it added.

Then, in a surprisingly passive-aggressive follow-up tweet, Deutsche Bahn revealed the teen had not spent the entirety of her journey sitting on the floor, stating: “It would have been even nicer if you had also reported how friendly and competently our team served you at your seat in first class.”

Thunberg was forced to clarify the situation, tweeting: “Our train from Basel was taken out of traffic. So we sat on the floor on 2 different trains. After Göttingen I got a seat.

“This is no problem of course and I never said it was. Overcrowded trains is a great sign because it means the demand for train travel is high!”

The incident had echoes of Labour Party leader Jeremy Corbyn’s celebrated “Traingate” spat with Virgin Trains in August 2016, in which he claimed to have been forced to sit on the floor of a “ram-packed” carriage as a direct consequence of the privatisation of the railways in the 1990s, only for the operator to release CCTV footage of the politician walking straight past available seats and accusing him of engaging in a political stunt.

Thunberg is currently crossing Europe by rail on her way back from the ultimately disappointing COP 25 UN climate conference in Madrid, having previously spent several months in the United States after crossing the Atlantic by solar-powered catamaran to minimise her carbon footprint.

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She was named Time magazine’s Person of the Year last week for her efforts to persuade world leaders to do more to battle climate change, an honour that saw her attacked in petulant style by jealous fellow nominee Donald Trump.