Tim Farron has insisted the government needs to be accountable to the public over the deal to be negotiated with the EU, and Britain can't afford to "jump out a plane without a parachute."
The Liberal Democrat leader was speaking to Julia Hartley-Brewer as the row over MPs' right to vote on Article 50 drags on.
Farron has previously condemned Theresa May for her announcement that Article 50 will be triggered in March 2017.
"Most people who campaigned to leave said this was about reclaiming sovereignty for Parliament and the UK," he told Julia Hartley-Brewer. "Then the first thing that happened is the unelected government stole this from Parliament and the people as to how we go forward.
"I don't think those who voted Leave would allow a handful of people to go and stitch up a deal without accountability or scrutiny.
"If you trigger Article 50 without knowing what deal you can secure, you are jumping out of a plane without a parachute and that is foolish."
The conversation then descended into an argument between him and our mid-morning presenter. Listen to it above.