Nick Clegg said the issue of immigration was "the biggest dividing line in politics today" and branded plans for a cap "arbitrary", "pointless" and "distracting".
In an article for The Sunday Times (£), Mr Clegg wrote:
Sticking a big no-entry sign on the cliffs of Dover may be politically popular, but at a huge economic cost. What would happen if tonight every European living in the UK boarded a ship or plane and went home?
Are we really that keen to see the back of German lawyers, Dutch accountants or Finnish engineers? Do we want the NHS to fall over and the City of London to grind to a halt?
Britain would be one step closer to the exit, even though walking away from Europe would cripple the economic recovery that's been so hard won.
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The referendum story is rapidly heading south. Scottish voters were promised more power - now English and Welsh voters ask "what about us?"
The Scottish independence referendum was threatening to turn into a huge boost for separatist movements in many countries in Europe.
A sigh of relief across Westminster and a crushing sense of disappointment for 45% of Scotland, but Yes campaign could not have done more.