The blunder became evident after the former Mayor of London claimed during the debate that large movements of labour across the EU “have a compressing effect on wages”.
But Alex Salmond, the former Scottish First Minister who was on the panel arguing the case to Remain in the EU, asked: “Who in the Bank of England said that?”
Mr Johnson replied: “It was a Bank of England study that showed that for every 10 per cent increase in immigration there was a two per cent reduction in wages”.
Mr Salmond, however, continued to interrogate the former London Mayor. He asked: “Have you read that study Boris? Have you actually read it,”
After a short silence, Mr Johnson replied: “I have not read that study”.
Mr Salmond added: “Can we just nail this because I’ve heard this from a number of people. So I’ve taken the trouble of reading the study… it says a 10 per cent rise in immigration would result in a one third of one pence diminution in average wages. One third of one pence."
It comes as Lord Stuart Rose, the chair of the Remain campaign, said he had been misquoted over claims wages would go up if Britons voted to leave the EU – adding they would in fact go down.
He told the Guardian: “I would say this, wouldn’t I, but I was misquoted. I was asked a straight economic question … which is if labour goes down in availability, what happens to the cost of labour and the answer is simple economics, the cost of labour goes up.
“But that is not anything to do with the actual argument about whether we should or shouldn’t be in the bigger community. What we really have to be sure about is a continually growing economy, which I believe we have more chance of doing in a 500 million-person community and the largest economic bloc in the world.
Speaking at the online debate, Mr Salmond also quoted the SNP manifesto for last month's Holyrood elections which stated that the parliament should have the right to hold a new referendum if a UK poll saw Scotland taken out of the EU “against her will”.
"You don't know the result of a referendum in advance, but what we do know is that the SNP stood on that manifesto in last month's election and got 47% of the vote in Scotland.
"Now, this referendum we are having just now was held by David Cameron on a mandate of 37% of the vote.
"So, it would have to go through the Scottish Parliament. It would have to be a Remain vote in Scotland, accompanying a Brexit elsewhere, but under these circumstances, the answer to your question is yes," Mr Salmond said.
The comments appear in contrast to Scottish First Minister Nicola Sturgeon's stance that she is only interested in campaigning for a Remain vote and will not speculate on possible political repercussions of Brexit.
The EU referendum debate has so far been characterised by bias, distortion and exaggeration. So until 23 June we we’re running a series of question and answer features that explain the most important issues in a detailed, dispassionate way to help inform your decision.
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