The British House of Commons has voted for a bill not to leave the European Union without an agreement.
Johnson has pledged to call early elections in mid-October, if the bill is passed.
Johnson urged opposition lawmakers in the House of Commons to support his plan to hold early elections, adding that the British government had made significant progress in plans to exit the EU without an agreement.
This was preceded by a House of Commons majority vote in favor of the second reading of the bill, which would prevent the prime minister from adopting a Brexit without an agreement. 329 deputies voted in favor and 300 against.
On the first reading, the House of Commons voted by 328 votes to 301 to control the agenda, which means that a bill seeking to delay the exit date could be introduced.
Johnson's defeat was made possible by the defection of 21 conservative MPs and their vote alongside Labor opposition deputies.
The most prominent lawmakers who rebelled against the prime minister's will and voted for the opposition include Nicholas Sums, grandson of late Prime Minister Winston Churchill, Philip Hammond, a former finance minister, and Johnson has vowed to expel all 21 Conservative lawmakers.
After the vote, Johnson formally tabled a memorandum calling for early general elections in mid-next month.
Johnson needs the approval of two-thirds of the members of parliament to pass a memorandum calling for early elections, but opposition leader Jeremy Corbin said his deputies would not vote for her until the bill passed out of the House of Lords and passed the Queen's approval making it a binding law.
Johnson said Monday that the chances of a deal between London and Brussels are high, and warned that if MPs vote to delay the exit, they undermine Britain's negotiating position and make any other negotiations impossible.