Jeremy Corbyn has urged the Cabinet to "stop fighting" and spell out what it wants from Brexit.
The Labour leader spoke after Brexit Secretary David Davis dismissed suggestions Britain was heading for a "Max Mad-style" dystopia after leaving the European Union and committed to maintaining high regulatory standards.
Responding at the EEF manufacturers' conference, Mr Corbyn said: "We are leaving the EU, but our businesses must not be forced to withdraw from European markets.
"Business needs clarity and with four out of six of the Government's "Road to Brexit" speeches already delivered, it seems to me their approach to Brexit is, if anything, less clear.
"It's time for the Cabinet to stop fighting and the Government to say where it wants to take the country."
Open Britain supporter and Labour MP Wes Streeting said the Government's "real agenda" was lower standards, weaker protections and "a desperate scramble for free trade agreements" with the likes of US President Donald Trump.
He went on: "Would you trust the likes of Boris Johnson, Liam Fox and Jacob Rees-Mogg to protect rights at work, environmental standards and restrictions on bankers' bonuses, after their false promises on £350 million extra a week for the NHS? That is what David Davis is asking the public, and the EU, to do."
TUC general secretary Frances O'Grady said: "David Davis lacks a plan to deliver a 'race to the top'. And many of his Conservative colleagues say that they want 'Mad Max' cuts to workers' rights and consumer standards.
"To prove his intentions, the Brexit Secretary should keep staying in the single market on the negotiating table. Of all the current options, it's the best platform for a race to the top, and the best protection against a race to the bottom."
Tim Roache, general secretary of the GMB union, said: "Since 2010, the Conservatives have repeatedly chiselled away at vital protections and workplace justice describing them as 'red tape' or 'a burden' on business.
"Theresa May has even made ministers of people who think British workers 'are among the worst idlers in the world'.
"How on earth can we rely on them to safeguard workers' rights?"
Industry leaders welcomed Mr Davis's commitment not to undercut EU rules, and therefore remain at least aligned with them.
EEF chief executive Stephen Phipson said: "UK manufacturers have long called for the UK to seek high alignment on technical regulations and standards with the EU to protect current trading relationships after its transitional period following Brexit.
"The Secretary of State is right to say that the future economic partnership must include a mechanism to manage regulatory co-operation and recognises the ongoing importance and competitiveness in our sector and is clearly in the national interest and the interest of our closest partners in Europe."
Adam Marshall, director general of the British Chambers of Commerce (BCC), said: "The Government's commitment to maintaining high standards following the UK's departure from the EU is an important step on the road toward greater clarity for business."
He appeared to call for regulatory alignment with the EU, which Brexiteers fear would mean leaving in name only.
Mr Marshall said: "UK firms would welcome a pragmatic agreement between the UK and the EU that ensures businesses face only one set of regulatory approvals to sell their goods across borders.
"This is important to ensure business continuity and effective supply chains on both sides of the English Channel, in industries from cars to cables."
British Retail Consortium chief executive Helen Dickinson said Mr Davis's assurances on maintaining and improving standards were "welcome".
But she added: "With a crucial month ahead in the Brexit negotiations, this is the time to provide greater certainty to businesses and consumers on how a framework of mutual recognition of standards and as 'frictionless trade as possible' will shape the UK's future relationship with the EU."
Anthony Walker, deputy CEO of techUK, called for alignment of rules around data protection and electronic standards.
"It is in the interests of both tech businesses and their consumers that the UK maintains high regulatory standards after Brexit," he said.
"Being aligned with the EU in these key areas will be essential for enabling UK firms to trade and compete fairly for business across Europe."