The deployment includes 16,000 British army troops who will be based in Eastern Europe from February to June, an aircraft carrier strike group, F35B Lightning attack jets, and surveillance planes.

Nato’s Exercise Steadfast Defender 24 marks the Western alliance’s 75th year.

“I can announce today that UK will be sending some 20,000 personnel to take part in one of Nato’s largest deployments since the end of the Cold War,” defence secretary Grant Shapps said in excerpts of a speech due to be delivered later today at Lancaster House, published by the defence ministry.

The Nato alliance has boosted the number of combat-ready troops after Russia’s president Vladimir Putin ordered the invasion of Ukraine almost two years ago and has continued to support Kyiv with military, economic, and humanitarian aid.

“It will see our military joining forces with counterparts from 30 Nato countries plus Sweden, providing vital reassurance against the Putin menace,” Shapps said about the exercise.

Last week, Prime Minister Rishi Sunak announced that the UK will increase its support for Ukraine in the next financial year to £2.5 billion, an increase of £200 million on the previous two years.