LONDON, Dec. 4 (Xinhua) -- British Prime Minister Theresa May on Tuesday launched her last-ditch efforts to sell her Brexit deal to MPs, saying that "it is parliament's duty to deliver Brexit" as she opened the five-day parliamentary debate on Britain's departure from the European Union before the historic vote on Dec. 11.

The prime minister insisted that her Brexit deal, reached between London and Brussels last week, is the only choice on the table for the parliament, saying that the choice for MPs is "this deal, no deal or no risk of no Brexit."

"I am speaking to each (parliament) member and every party that this deal deserves your support," she said, calling for a unity in parliament so that "we will pass the test history has set us today."

The prime minister described the Britain-EU deal as an "honourable compromise" after more than two years of hard negotiations.

Meanwhile, May also dismissed the increasing calls for a second referendum, saying that "the second referendum will worsen divisors" in the country, which has been already divided since the 2016 referendum.

The prime minister said Brexit divisions had become "corrosive" to British politics and the public believed the issue had "gone on long enough" and must be resolved.

The prime minister's statement came in the worst day in her political life shortly after she has suffered three Brexit defeats in the House of Commons before the five-day debate kicked off.

In a speech repeatedly interrupted by MPs attacking her deal, the prime minister pledged to give the parliament and the devolved administrations a "greater and more formal role" in forthcoming negotiations with the EU over trade.

However, she declined to say whether MPs would get a vote on that deal.

By a vote of 311 to 293, the parliament forced the British government to publish its full legal advice on the deal. MPs voted to blame the government in contempt of parliament for just issuing a summary, rather than the full text as required by a parliamentary decision last month.

It is the first time for MPs to hold the government in contempt of the parliament in the country's modern history.

MPs also backed calls for the House of Commons to have a direct say in what happens if her deal is rejected next Tuesday.

On Tuesday evening, the pound nosedived after the British government said it will publish full legal advice on the Brexit deal in the wake of the parliamentary vote.

Shortly after the vote, the pound crashed to its lowest since June 2017, falling by 0.5 percent against the U.S. dollar to 1.2659 before rallying slightly.

In response, Jeremy Corbyn, leader of the opposition Labour Party, told the parliament that the prime minister's Brexit deal "will make Britain worse off."

Rejecting the government statement that Brexit will help Britain take back control of sovereignty, money and jobs, Corbyn said, "This government is not taking back control, it is losing control."

The opposition leader went further to ask the government to resign and called for a general election.

"This government can not govern, so it should make way to (general) election," Corbyn said.

He said that his fellow Labour MPs will vote against the Brexit deal on Tuesday, and "we will force the British government to go back and negotiate" with the European Union.

"We respect referendum result but reject the deal," he said, adding that "our vote is our veto."

At the same time, Corbyn did not buy the prime minister's statement that the parliament's failure in supporting her Brexit deal will risk no-deal divorce, saying "No deal is not the real option."

For his part, Boris Johnson, former foreign secretary who resigned in July to protest May's Brexit plans, said in the parliamentary debate that he will also vote against May's Brexit deal.

"This deal is a national humiliation," Johnson said. "The government's heart is not in the deal."

"We must be clear that we will not accept backstop," he said, referring to the Britain-EU arrangement on the place of Northern Ireland in the single market and customs union after Brexit in March next year.

The Tuesday vote was a triple blow for the prime minister after MPs were also given more powers over a plan B if her deal is not voted through the Commons next week.

This could open the door for the Commons to throw its weight behind a Norway-style soft Brexit or even a second EU referendum, though prominent Leave-backing MPs questioned whether any such vote would be binding on ministers.

Labour's shadow Brexit secretary, Keir Starmer, said the finding of contempt was "a badge of shame" for the current government, with "huge constitutional and political significance."

"By treating Parliament with contempt, the government has proved it has lost its majority and the respect of the House," Keir said.

"The prime minister can't keep pushing Parliament away or avoiding responsible scrutiny," he said.