The Government has been accused by a parliamentary inquiry of "sleep-walking" into the crisis over Ukraine.

The EU Committee of House of Lords found there had "catastrophic misreading" of mood by European diplomats in the run-up to the stand-off between Russia and the West.

Despite Britain's role as one of the signatories to an international agreement assuring the territorial integrity of Ukraine, it said the Government "has not been as active or as visible as it could have been" in seeking to resolve the crisis.

The findings come as a further blow to David Cameron after Britain's former top Nato commander, General Sir Richard Shirreff, said the Prime Minister had become a diplomatic "irrelevance" in the crisis.

In a damning indictment of EU diplomacy, the committee said a decline in expertise on Russia in the Foreign and Commonwealth Office (FCO) and other EU foreign ministries had left them ill-equipped to formulate an "authoritative response".

It said that for too long the EU's relationship with Moscow had been based on the "optimistic premise" that Russia was on a trajectory to becoming a democratic country.

The result was a failure to appreciate the depth of Russian hostility when the EU opened talks with aimed at establishing an "association agreement" with Ukraine in 2013.

"It (the committee) believes that the EU, and by implication the UK, was guilty of sleep-walking into this crisis," said the committee chairman, Lord Tugendhat.

"The lack of robust analytical capacity, in both the UK and the EU, effectively led to a catastrophic misreading of the mood in the run-up to the crisis."

It was the decision of the pro-Russian president Viktor Yanukovych - under pressure from Moscow - to pull out of the talks with the EU which triggered the mass protests which led to his downfall.

Russian president Vladimir Putin responded by annexing Crimea and has been blamed by the West for fomenting the bloody revolt by pro-Russia separatists in eastern Ukraine.

The committee said that as one of four signatories to the 1994 Budapest Memorandum which pledged to respect Ukraine's territorial integrity, there had been a particular responsibility on the UK.

"The Government has not been as active or as visible on this issue as it could have been," it said.

It said that the FCO now needed to look at how it could rebuild its lost analytical capability on Russia.

"While there has been an increase in staff at the FCO to deal with Ukraine and Russia, we have not seen evidence that this uplift is part of a long-term rebuilding of deep knowledge of the political and local context in Russia and the region," it said.

"We recommend that the FCO should review how its diplomats and other officials can regain this expertise."

An FCO spokeswoman said no-one could have predicted the scale of the "unjustifiable and illegal" Russian intervention in eastern Ukraine.

She added: "The blame lies squarely with the pro-Russian separatists, backed by the Russian authorities, not with an Association Agreement between the EU and Ukraine which had been under negotiation for more than seven years before Russia decided to illegally invade and then annex part of its neighbour.

"The UK has played a leading role in supporting Ukraine's right to chart its own future by ensuring that the EU imposed tough sanctions on Russia for seeking to dictate these choices."

The spokeswoman said the FCO agreed with the committee that the EU must ratchet up sanctions if the situation in Ukraine worsens.

She added: "The FCO has strengthened its expertise on Russia and the region and will continue working to ensure a strong and united response to Russian aggression."