Mr Campbell Bannerman accused former defence minister Lord Davies of “ignoring” last June’s vote to leave the European Union and said a bad Brexit deal could cost the UK “billions more”.
Speaking on the World at One on BBC Radio 4, Lord Davies said the Prime Minister’s move to hold a General Election was an “ego trip” that had “blown up in her face”.
“It’s ironic because of course this election was really called by Theresa May as a sort of personal ego trip,” he said.
“She wanted a very substantial personal majority and I think it’s blown up in her face because she’s been shown to be very autocratic, not all together reliable and there is an irony there.”
But Mr Campbell Bannerman, who was Ukip deputy leader from 2006 to 2010, argued Mrs May was the “best person” to negotiate with the European Union.
David Campbell Bannerman said a "bad" Brexit deal could cost the UK "billions of pounds more"
If we don’t get a good deal, it could cost us billions more.
David Campbell Bannerman
He said: “I’m sorry I think you’re ignoring the biggest ever vote in British history which was the referendum.
“It’s a massive vote and Theresa May is going to be the best person to negotiate a great deal from the EU.
“If we don’t get a good deal, it could cost us billions more. That will compromise our security.”
Davies, who argued his point was about the upcoming General Election not Brexit, took issue with Mr Campbell Bannerman’s comments.
May meets Juncker and Barnier at Number 10 Wed, April 26, 2017
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Theresa May hosted European Commission President Jean-Claude Juncker and chief negotiator Michel Barnier at Downing Street for the first face-to-face talks since she triggered the two-year process of withdrawing from the EU
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Prime Minister Theresa May greets European Commission President Jean-Claude Juncker ahead of a working dinner at 10 Downing Street, London
“You must be joking,” he said.
The Conservative MEP interjected once again and replied: “No, I’m not joking. Why is it a joke, you think it’s a joke?”
Earlier today, the Conservatives lashed out at Jeremy Corbyn after the Labour leader called out Mrs May for refusing to attend Wednesday's leaders debate.
The veteran politician confirmed he would take part during a rally this afternoon, in which he criticised the Tories for what he called "a stage-managed arms-length campaign".
He said: “I will be taking part in tonight’s debate because I believe we must give people the chance to hear and engage with the leaders of the main parties before they vote."
Lib Dem leader Tim Farron, UKIP's Paul Nuttall, SNP deputy leader Angus Robertson, Green co-leader Caroline Lucas and Plaid Cymru leader Leanne Wood will also participate in the televised showdown.
But a Tory party spokesman confirmed there will be “no changes to the prime minister’s plans” regarding tonight’s debate.
Amber Rudd will still appear in place of Theresa May on the BBC show.