- The vote is a major boost for the prime minister's prospects of fulfilling his pledge to take the UK out of the EU by October 31.
- However, the narrow parliamentary majority for the deal spells trouble for its prospects of passing its final stages.
- Johnson has threatened to pull the bill altogether if MPs vote to delay its passage, or significantly alter its central purpose.
- Visit Business Insider's homepage for more stories.
Boris Johnson's Brexit bill has passed its first stage in the UK parliament, in a major boost to the prime minister's plan to take the UK out of the EU by October 31.
Members of Parliament voted on Tuesday evening to approve Johnson's Withdrawal bill in principle, setting up a frantic race to push it through its final stages before the end of the month.
The vote represents an important test of support for Johnson's Brexit plans, after his predecessor Theresa May failed on four previous occasions to gain the approval of MPs for her own deal.
MPs will on Wednesday begin the process of debating amendments to the bill, which have the potential to radically alter it, or wreck its prospects of passing altogether.
Among alternative plans being pushed by MPs are a bid to compel Johnson to negotiate retaining ties to EU customs rules after Brexit, as well as a push for a second referendum.
Another amendment designed to extend the 14 month transition period beyond 2020 is also gathering support among MPs.
Donald Tusk, the European Commission president, indicated on Tuesday that the EU was prepared to grant an extension of the October Brexit deadline until next year.
Tusk told the European Parliament: "The situation is quite complex following events over the weekend in the UK and the British request for an extension of the article 50 process...
"We should be ready for every scenario but one thing must be clear, as I said to prime minister Johnson on Saturday, a no-deal Brexit will never be our decision."
However, the prime minister on Tuesday insisted that any attempt to frustrate or delay Brexit would mean that he would pull the bill and "go forward to a general election," adding that the Brexit process could not be allowed to continue for "months" more of delay.
Sources close to Johnson suggested that he may be willing to accept a shorter delay of a matter of weeks in order to a ratify his deal, according to multiple reports.
What is in the Withdrawal Agreement Bill?
The Withdrawal Agreement Bill is designed to give legal effect to the Brexit deal negotiated by Johnson and allow Britain to legally leave the EU, while entering a 14 month transition period.
The bill is based on a previous agreement negotiated by Theresa May but with significant differences in the relationship between Northern Ireland and the rest of the United Kingdom.
Under the agreement Northern Ireland would remain tied to EU customs rules after Brexit.
This measure has proved hugely controversial because it will mean new checks in the Irish Sea, something that has outraged unionists in Northern Ireland.
Other aspects of the deal include provisions for the UK to pay its 39 billion "divorce bill" to the EU as well as provisions to maintain the rights of EU citizens living in the UK after Brexit.
Opponents of the bill are concerned about several other aspects of the agreement, including provisions which would allow the prime minister to take Britain out of the EU without a deal at the end of the transition period.