Brexit Secretary David Davis kicked off two days of debate on the second reading in the House of Commons of the officially-titled European Union (Notification of Withdrawal) Bill.
If passed, the Bill will hand Theresa May the authority to trigger Article 50 of the Lisbon Treaty and start EU divorce talks.
She has vowed to invoke Article 50 by the end of March.
Beginning proceedings, Mr Davis said: "This Bill responds directly to the Supreme Court judgement and seeks to honour the commitment the Government gave to honour the outcome of the referendum held on June 23 last year.
"It is not a Bill about whether or not the UK should leave the EU, or indeed how it should do so.
“It is simply about Parliament empowering the Government to implement a decision already made, a point of no return already passed.
“We asked the people of the UK if they wanted to leave the EU; they decided they did.
"So at the core of this Bill lies a very simple question: do we trust the people or not?"
The Brexit Secretary told MPs the "democratic mandate is clear" for them to pass the Bill.
He said: "The electorate voted for a Government to give them a referendum. Parliament then voted to hold a referendum, the people then voted in that referendum and we are now honouring the result of the referendum as we said we would.
"This is the most straightforward possible Bill necessary to enact the referendum result and respect the Surpeme Court judgement."
Mr Davis also reminded MPs the House of Commons has "already overwhelmingly passed a motion to support the triggering of Article 50 by March 31" in a vote last year.
Speaker John Bercow revealed 99 backbenchers are hoping to speak in the debate today alone.
David Davis opened the Article 50 debate today
At the core of this Bill lies a very simple question: do we trust the people or not?
Despite the June 23 vote to quit the EU, Labour's shadow Brexit secretary Sir Keir Starmer responded to Mr Davis by claiming the Article 50 Bill is "very difficult" for Labour.
He said: "We have before us a short Bill and a relatively simple Bill. But for the Labour Party this is a very difficult Bill."
Sir Keir's comments sparked laughter on the Conservative benches, with Sir Keir forced to ask Tory MPs to "be courteous as I try to set out the position of the Labour Party in what are very difficult circumstances".
He added: "We are a fiercely internationalist party, we're a pro-European party. We believe that through our alliances we achieve more together than we do alone.
"We believe international co-operation and international collaboration and we believe in the international rule of law.
"These beliefs will never change."
Veteran Tory MP and europhile Ken Clarke was applauded by Labour and SNP MPs as he told the House of Commons he would be voting against the Bill.
The 133-word Bill follows the Supreme Court's ruling last week the Prime Minister must first gain the consent of MPs and peers before beginning EU exit negotiations.
The Liberal Democrats, SNP and rebel Labour MPs will this week introduce five wrecking amendments aimed at derailing the Bill.
Each of these amendments will be debated over the next two days, with votes to be held tomorrow.
But it has been reported Government ministers and Tory MPs have also been told to stay in the House of Commons until midnight tonight amid fears of an “ambush” late-night vote by pro-Remain MPs.
Labour will only try to introduce their planned seven official amendments at a later stage in the process and not this week.
Party leader Jeremy Corbyn has ordered his MPs not to block Brexit but could face a rebellion by up to 100 MPs.
If the Bill survives unscathed, it will return to the House of Commons for a third reading and a final vote on February 8, when it will then pass to the House of Lords.