Mr Tusk, a former Polish prime minister, has returned to politics in his native land since stepping down from the EU, and and did not mince his words when it came to the pipeline.

“From the point of view of the interests of the European Union, Nord Stream 2 is a bad project,” he said.

Spokesmen for Mrs Merkel did not comment on the claims on Monday but they came as it emerged that her government is spending its final days in power defending the divisive pipeline.

The veteran chancellor is set to stand down after 16 years in power next week, when a new coalition headed by Olaf Scholz takes office.

But documents obtained by the website Axios show that Mrs Merkel’s government is still lobbying the US Congress not to impose sanctions against companies involved with Nord Stream 2.

The US has long opposed the pipeline, arguing it will leave Europe too dependent on Russia for its energy needs and allow Vladimir Putin to isolate Ukraine by cutting the flow of gas across its territory.

President Joe Biden agreed to waive sanctions against German companies earlier this year to avoid a confrontation with a US ally.

He and Mrs Merkel agreed a deal in July under which Germany pledged to take action if Russia ever seeks to use energy as a weapon.

Many argue Mr Putin is already doing so, after he cut gas supplies to western Europe, sending prices soaring in the run-up to winter.

Mr Scholz’s government has yet to take a stance on the pipeline. Annalena Baerbock, the incoming foreign minister, has opposed it in the past, but Mr Scholz is thought to favour it.