Labour leader Jeremy Corbyn has distanced himself from calls for a second referendum, saying it was an "option for the future" but not one for "today".
Speaking to Sky News, Corbyn said his party would vote against the draft withdrawal agreement because it failed to meet Labour's six tests, one of which is that it must guarantee the same benefits as current EU membership.
The Labour leader also said that if there was another referendum, he did not know how he would vote.
Corbyn added to criticism of May's deal, branding it "one-way agreement" where the EU "calls the shots".
He said it did not "serve the interest of this country" and should be renegotiated by the government – something EU leaders have ruled out. Labour would focus on negotiating a permanent customs arrangement with the EU, he said, to prevent the UK from losing out on jobs, investment and economic development.
Corbyn has appeared lukewarm to the idea of a second referendum, repeating his stance that Brexit can't be stopped, a view that contradicts a number of his MPs who have backed a second vote.
He has clashed with his shadow Brexit secretary Keir Starmer who has said "all options must be on the table", including a second referendum with an option to remain in the EU.
Starmer said last week that threats of either accepting May's deal or leaving the EU without a deal were a "political hoax" and that MPs were not duty-bound to vote in her favour.
He told the Observer today that he was working across parties to prevent a no-deal Brexit by making amendments to legislation that would make such an outcome impossible.
“There are plenty of Conservative MPs who have come up to me to say that they will not countenance the UK crashing out of the EU without an agreement," he said. "There is a clear majority in parliament against no deal, and Labour will work across the Commons to prevent no deal. On the government’s own analysis, over 50 changes to legislation would be needed for a no-deal outcome, so there will be no shortage of opportunities to pass binding votes on this issue.”
Meanwhile, shadow attorney general Shami Chakrabarti told the BBC that May's draft deal was "the worst kind of bureaucratic fudge" that did not satisfy anyone.
She repeated calls for a general election, saying that if Labour was to assume power there would be a "completely different atmosphere" in negotiations that would allow it to strike an alternative to the deal reached by May.