Scottish-style devolution has been suggested as an option for Crimea by a former Russian oligarch.
Mikhail Khodorkovsky's comments came as David Cameron said Sunday's referendum on whether it should join Russia is illegal, unlike the Scottish independence poll.
Mr Khodorkovsky, who was released by Putin in December after a decade in jail, said that giving Crimea the kind of autonomy from Ukraine that Scotland had inside the UK could ease regional demands for union with Russia, whose forces took over the peninsula a week ago.
"The best option might be to keep Crimea within Ukraine but with the broadest possible autonomy; for example, akin to what Scotland has within Great Britain," he said yesterday.
Mr Cameron underlined how the 28 nations of the EU were "clear and united" that Russia's actions were "in flagrant breach of international law and will incur consequences" but he stressed how there was "still an opportunity for Russia to resolve this situation diplomatically".
A meeting of EU foreign ministers on Monday is likely to be key to the West's response.
In Commons exchanges, Tory veteran Sir Peter Tapsell, asked: "Why is it acceptable for the Scottish Nationalists in Scotland to be granted a referendum on constitutional arrangements dating back to 1707 but unacceptable for Russian Nationalists in the Crimea to have a referendum about constitutional arrangements only dating back to 1954?"
The PM replied: "The difference between the Scottish referendum and the Crimea referendum is the Scottish referendum is legal.
"It was discussed and debated in this House and in the Scottish Parliament.
"We went a long way to put in place arrangements which I described would not only be decisive and fair but also legal. The difference with this referendum is that it's illegitimate and illegal under the Ukrainian constitution."
Officials from the UK and other western governments will today meet in London to draw up a list of top Russians who could face a travel ban and asset freeze if Moscow fails to de-escalate the Ukrainian crisis
The list would not include Russian President Vladimir Putin and were unspecific on whether key politicians or business people would be included on the list but one made clear it would go "beyond just categories".
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