Theresa May should give a "clear direction of travel" over her Brexit plans so businesses can properly prepare for the UK's split from the EU, Leave Means Leave has argued.
John Longworth, the former British Chamber of Commerce (BCC) chief who co-chairs the pro-Brexit campaign, also told IBTimes UK that such a move could strengthen the government's negotiating position with Brussels.
"All of sudden the balance of power, in terms of negotiating power, would shift radically...the boot would be on the other foot," he said.
That is because Longworth wants May and her ministers to indicate that the UK is planning to break from the EU's single-market and customs union.
His comments on Tuesday (7 December) came just before the government announced it would back a Labour motion, which calls for more "clarity" from May over her Brexit plans.
The government has tabled its own amendment to the motion, adding that Article 50, the official mechanism to split from the EU, should be triggered by the end of March 2017.
MPs will debate the motion in the House of Commons on Wednesday.
The move came as May faced a rebellion of up to 40 Conservative MPs who planned to back Labour's original motion.
Despite his calls for a "clear direction of travel", Longworth warned the government about revealing too much.
"I think the government shouldn't reveal its detailed negotiating position one iota because if you go into a business negotiation to tell the other side what your plans are would be very, very foolish," he said. "It's rather stupid of parliamentarians to think that would not be the case."
The EU's chief Brexit negotiator Michael Barnier revealed on Tuesday that he expects a deal between the bloc and the UK to be agreed in October 2018 and ratified in March 2019.
Longworth said he was "on the same page" with the EU on the timetable. "We have to execute the thing within a reasonable time scale and I'm very much favour of a clean Brexit," he said.
Shadow Brexit Secretary Sir Keir Starmer, who will be leading the debate in the Commons on Wednesday, said: "Labour's focus has always been on getting an assurance from the government that a basic plan for Brexit will be published before Article 50 is invoked.
"The victory today is that the government have now finally accepted Labour's call and committed to publish a plan.
"The government now need to focus on ensuring that plan delivers a sensible Brexit deal that protects jobs, the economy and living standards. Labour will hold them to account on this every step of the way."