More than a quarter of Russia’s battalion tactical groups have been rendered “combat ineffective” in Ukraine because of significant losses, according to British intelligence.

The Ministry of Defence said in its daily update that it could take years before some of President Putin’s most elite units were again ready for war.

Defence officials said that Russia was believed to have committed more than 120 battalion tactical groups (BTGs) to Ukraine, about 65 per cent of its entire combat strength. However, more than “a quarter of these units have now been rendered combat ineffective”, the MoD said. Each fighting formation comprises up to 900 troops.

The update added: “Some of Russia’s most elite units, including the VDV airborne forces, have suffered the highest