Wales' first minister has said the UK government has been dragged "kicking and screaming" to a "sensible" approach to relations with the EU after Brexit.
On Thursday a white paper fleshed out the Chequers agreement that sparked the resignations of Boris Johnson and David Davis from the cabinet.
Some Brexit supporters argue it follows EU rules and regulations too closely.
Carwyn Jones said he gave the blueprint a "cautious welcome" but claimed the customs plans were "unworkable".
The long-awaited White Paper is aimed at ensuring trade co-operation, with no hard border for Northern Ireland, and global trade deals for the UK.
"The UK Government's White Paper is a significant change of direction which moves away from their red lines towards the negotiating position we set out in January last year," the first minister said.
"It is a source of regret that the UK Government has, again, had to be dragged kicking and screaming to this sensible approach, but today's movement must at least receive a cautious welcome.
"However, far too many questions remain unanswered and some proposals - such as a twin track customs systems - appear unworkable.
"I fail to see why the UK Government choose to pursue such an overly bureaucratic and clumsy approach to trade, when continued participation in the Single Market and customs union would resolve these issues, protect jobs, trade and investment and provide the certainty and stability business needs."
Mr Jones said he would discuss the proposals with the EU's chief negotiator Michel Barnier in Brussels on Monday.
The first minister said he would urge the other 27 member states to adopt a flexible approach in order to avoid a "catastrophic no-deal scenario".
Plaid Cymru MP Jonathan Edwards - whose party wants to stay in the single market and customs union - accused ministers of still trying to "cherry-pick" certain aspects of EU membership despite opposition from Brussels.
"For two years the EU has repeated that we cannot have our cake and eat it and it is deeply irresponsible for the UK Government to continue to ignore their warnings so close to the deadline.
"The longer the UK Government goes on deluding itself with these fanciful and undeliverable proposals, the more damage will be caused to our economy."
Meanwhile Monmouth Conservative MP David Davies - who backed Leave - called on his fellow Eurosceptic Tories to "swallow their pride" and back Theresa May's plan as the best course of action available.