Lord Menzies Campbell compared the tactics of those seeking a leave vote in the EU referendum to the controversial comments of Republican presidential hopeful Donald Trump.
Lord Campbell, head of the European Movement in Scotland, called for the Brexit campaign to tone down its language on immigration or risk long-term damage regardless of the result.
He urged the Remain campaign to refocus the debate on the the benefits of migration from the EU to the UK, emphasising University College London research showing European migrants made a net contribution of £20 billion to UK public finances between 2000 and 2011.
Lord Campbell also highlighted that the 1.6 million UK citizens living in the rest of the EU are routinely described as “ex-pats”, not “migrants”.
He said: “As the Remain side, we must robustly seek to promote the benefits that migrants from other parts of the EU have brought to the UK.
“We know that they make a major contribution to the economy, as well as socially and culturally, and what we are seeing is a deliberate stoking-up of fears and prejudice in a desperate attempt to boost support for Brexit.
“There are similarities between the tactics being used by the leaders of the Brexit campaign and Republican presidential candidate Donald Trump on immigration.
“To counter this we need to go on the offensive and highlight the positive benefits that migrants bring to this country.
“The language we are hearing is extremely ugly and the danger is that race relations in this country will be permanently challenged if the positive case is not set out and the rhetoric toned down, whatever the result.”