Former party leaders Ed Miliband and Nick Clegg are among a group of MPs from across the political spectrum calling for a parliamentary vote on Brexit.
The group, which also includes pro-EU Tories, SNP and Green party politicians, is seeking clarity on a so-called hard Brexit that would mean leaving the Single Market and which Prime Minister Theresa May this week indicated the country was heading towards.
Read more: A hard Brexit could cost up to 75,000 jobs
“Having claimed that the referendum was about returning sovereignty to Britain, it would be a complete outrage if May were to determine the terms of Brexit without a mandate from parliament," Miliband told the Observer.
“There is no mandate for hard Brexit, and I don’t believe there is a majority in parliament for [it] either. Given the importance of these decisions for the UK economy … it has to be a matter for MPs.”
MPs are considering tabling an urgent question in parliament to get answers on the matter, the newspaper reports.
The move follows huge concern from across the business world over signals that the government will push forward with limits to immigration, sacrificing membership of the Single Market in the process.
Business groups yesterday called on the government to work with business on the terms of negotiating Brexit, urging "barrier free access to the EU's Single Market, which is vital to the health of the UK economy".
Tory MP and former education secretary Nicky Morgan said there were a "sizeable number" of colleagues in the party who held the same view.