Mrs Merkel’s recent incidents of tremors in her limbs when attending high-profile public events have led to fears over her health and, according to one report, piqued the interest of spy agencies. The Bild Am Sonntag newspaper said yesterday: “One leading western intelligence service is certain: that the health problem of the German chancellor ‘is a neurological problem’.”

The chancellor, 64, appeared unsteady and was seen shaking at two events in Berlin eight days apart and was asked about the problem at a G20 summit in Japan this weekend.

“I’m fine,” Mrs Merkel insisted, with “nothing in particular to report”. She added: “I’m convinced just as this reaction occurred it will go away again.”

Annalena Baerbock, leader of the German Greens, linked Mrs Merkel’s tremors to the European heatwave, which some environmentalists have blamed on climate change.

“We can see from the chancellor it is clear that this summer climate has health consequences,” she said. “Anyone who stands in the sun for an hour would get shaky … The heat doesn’t stop for chancellors either.”

Ms Baerbock, 38, apologised and said that she had “thoughtlessly made a connection that doesn’t exist”, adding: “This was a mistake.”