Last week Mr Johnson said that European nations must choose between “mainlining” Russian gas and defending peace in Ukraine. 

“When we say that we support the sovereignty and integrity of Ukraine that is not because we want to be adversarial to Russia, or that we want in some way strategically to encircle or undermine that great country,” Mr Johnson said.

“We hope that our friends may recognise that a choice is shortly coming between mainlining ever more Russian hydrocarbons in giant new pipelines, and sticking up for Ukraine and championing the cause of peace and stability, let me put it that way.”

Earlier on Tuesday Defence Secretary Ben Wallace visited Ukraine to “reaffirm Britain’s enduring support” for their sovereignty and territorial integrity. 

Nord Stream 2 said it had been notified by the regulator. “We are not in a position to comment on the details of the procedure, its possible duration and impacts on the timing of the start of the pipeline operations,” it said in a statement.

The Kremlin was not immediately available to comment.

The intervention came as Russian troops continued to gather near Ukraine, prompting fears of an imminent invasion, and tensions over migration escalated at the Polish-Belarus border.