Labour leader Jeremy Corbyn believes the Government are in danger of wandering into a "cliff edge Brexit".
Corbyn's comment come following Sir Keir Starmer outlining Labour's shift in policy when it comes to staying in the single market and customs union during a transition post-Brexit.
Corbyn, who has just completed a five-day tour of Scotland, said: "This is a transitional arrangement, that he [Sir Keir] is suggesting that it's the Government that has confusion. It restarts the negotiations tomorrow, and it seems to me they're in danger of wandering into a 'cliff edge Brexit'.
"Ours is to protect jobs and protect working conditions in the transition."
Labour confirmed on Sunday it would be committing itself to continued UK membership of the EU single market and customs union during a transition period following the Brexit date of 2019.
Shadow Brexit secretary Sir Keir says Labour would stick with the "same basic terms" of Britain's current EU membership during the transition, which could potentially last five years.
In an article for The Observer, Sir Keir stated that the party is open to negotiating new single market and customs union term which the UK to agree to on a permanent basis.
Critics of continued customs union membership argue that it would prevent the UK from striking new trade deals with non-EU countries.
Labour promised prior to June's general election to seek to "retain the benefits" of the single market and customs union as part of a "jobs-first" Brexit, but leader Jeremy Corbyn has not said he would support continued membership beyond the date of Brexit.