London Mayor Boris Johnson has compared fears of economic uncertainty if Britain left the EU with the false panic over the computer 'Millennium Bug' in 1999, dismissing suggestions that a Brexit could be damaging for the UK as 'scaremongering'.

Johnson, a leading figure in the campaign for Britain to leave the EU, was grilled in Parliament by the Treasury Committee on Wednesday (23 March 2016) regarding the pros and cons of a possible Brexit.

Asked how long any period of uncertainty would be should Britain leave the EU, Johnson said: "I don't think there need be a period of uncertainty at all. I think the best analogy I can come up with this whole debate, is the Millennium Bug, the Y2K alarmism.

"People said that planes would fall from the sky and that computers would crash and the economy would tank by five percent or something. Nothing of the kind took place, I think there is a great deal of scaremongering and alarmism," he said.

Video: What you need to know about the EU referendumIBTimes UK

He said he would not want Britain to remain in the single market and would hope that Britain could negotiate separate trade deals with European Union countries.

"What is the evidence that there will not be an economic shock? I can simply revert to all the arguments that were made at the time of the euro decision," said Johnson before he was cut off by the committee chairman Andrew Tryrie and criticised for repeating himself too much.

An ICM poll released on 23 March put the campaign for Britain to leave the EU up by two percentage points. Support for Brexit rose to 43%, which is the highest proportion in favour of a British exit since ICM started its referendum tracker in May 2015.