Boris Johnson 'literally making it up' on Brexit

Cameron accused Boris of "literally making it up"
David Cameron has accused Boris Johnson of "literally making it up" when it comes to Brexit, referring to the Leave campaign's inability to say what an exit would look like. Commenting specifically on Johnson's claims that Britain could do a similar trade deal to the one Canada had he said:
"Canada is a country 4,000 miles away from the continent of Europe that does 10% of its trade with the EU. We are a country just 20 miles away from the continent of Europe and we do 50% of our trade with the European Union. So a Canada deal is not the right deal for us."
Johnson was also criticised by Peter Mandelson, who said he "doesn't really think Boris knows what he's talking about."