Labour will vote against Britain leaving the EU without a reaching a deal on the terms of its withdrawal, shadow Brexit secretary Sir Keir Starmer has said.
Speaking to ITV's Peston on Sunday, Sir Keir said: "I think it's blindingly obvious to everybody that we're not going to complete the whole final deal scenario within the two years for Article 50 and therefore we have a pretty stark choice.
"Either we go off the cliff with no deal which would be disastrous or we go on to sensible transitional arrangements," he added.
Labour has tabled a series of amendments that would bind the government to a transitional period after Brexit, during which the UK would in effect remain inside the single market and customs union.
Sir Keir said parliament should have a say on whatever the Article 50 deal is, adding "I hope it's a deal, and I hope it's got transitional in it".
He also insisted that there should be a vote in the event of a "no deal" which would be "disastrous and cannot simply be waived through".
"We want a vote on it and I can tell you we'll vote against it".
When asked if he thinks parliament would also vote against the UK exiting the European Union without an agreement, Sir Keir said: "I think the consensus would be against it."
He went on: "This casual talk of no deal...it means no deal on trade that means huge tariffs, it means no deal in Northern Ireland as to the border.
"It means no deal for EU citizens here and for UK citizens abroad. It means no deal on counter-terrorism."
"No deal is simply not viable," the Labour MP added.
Earlier, shadow chancellor John McDonnell suggested some Tory MPs are also are in talks with Labour to prevent Britain leaving the EU without a deal.
He also said he believed Theresa May lacks a majority in the House of Commons for no deal, adding he is "not willing to countenance" such an outcome.
Mr McDonnell also accused the Tories of "fighting among themselves" rather than negotiating with the EU.
"They're more interested in negotiating to save theConservative Party than they are in the interests of the country.
"That's why I think actually it's a disgrace. They should come to their senses, behave responsibly and look after the interests of the country."
In response, Brexit Secretary David Davis said while there was still much work to be done, discussions had made "significant progress" since June.