The repulsion of Russian tanks and troops in Kyiv and elsewhere had largely depended on air support, Mr Wallace said, which could not happen if a no-fly zone was imposed by Nato troops.

“There’s been a lot of no-fly zone suggestions and no one seems to actually analyse what ‘no-fly zone’ means and what it would mean for Ukrainian armed forces,” he told Times Radio.

“The Ukrainian armed forces are outnumbered on the ground massively by Russian armour and Russian army.

“One of the few weapons they have against the soldiers on the ground and forces like those big armoured columns is the ability to fly their fast jets and to use [drones] to strike logistical chains and air defences.

“If you have a no-fly zone, it will favour the force with the massive armed forces, which will be Russia because they will be able to carry on regardless.

“They also have lots of long-range missiles so they can substitute air attacks with missile attacks.”

He also repeated the Government’s position that enforcing a no-fly zone with Nato jets created the possibility of Western forces directly engaging Russia in combat.

Such an event would trigger Nato’s collective defence agreement, escalating the situation to a full-scale war between Putin and the West, ministers believe.

“If you have a no-fly zone you have to enforce a no-fly zone,” Mr Wallace said in a separate interview with Sky News.

“That would involve British fighter jets shooting down Russian fighter jets, probably over Ukraine, that would lead to Article Five triggering of Nato and Nato is a self-defence pact.

“All 30 countries will come to each other’s aid, the triggering of Article Five would lead to a war against Russia across the whole of Europe.”

Britain’s preferred strategy has been to arm the Ukrainian military, including drones and anti-tank weapons, to beat back the invading force.

On Wednesday, Mr Wallace was cautiously optimistic about Ukraine’s prospects in the war because of “huge amounts of low morale in the Russian forces” and “lots of surrenders”.

But he also warned that there was “no limit” to the violent means Putin would use.

“That doesn’t take away from the fact you have a very ruthless Russian armed forces leadership and a president who seems to know no limit to how much violence they will use to achieve their aims,” he said.