The UK needs to "pause and think" before doing something "irrevocably stupid" about Brexit, Jo Johnson said the day after he resigned as a minister.
On BBC Radio 4s Today, he again called for another referendum and said the offer was "spectacularly short" as promised.
The former Transport Minister said it would be a "democratic travesty" if no further vote took place.
He denied that his actions amounted to a coup against the prime minister.
Mr Johnson, who voted in favor of remaining in the EU in the 2016 referendum, resigned when Theresa May's future deal with Brussels was presented to Cabinet Ministers.
He warned the UK against the choice between "vassalage" under their proposals and "chaos" if it left the EU without an agreement.
The Orpington MP in Kent said he "happily made the decision" to end his own ministerial career, and when asked if he believed that other ministers would resign, he said, if they felt it was it is right to take a stand "good for her".