UK MPs are debating whether or not to overturn amendments to the European Union (Notification of Withdrawal) Bill.
These are linked to calls from peers to secure the rights of EU nationals living in the UK and guarantee a "meaningful" vote for Parliament on the final deal.
Here are select quotes from the debate:
:: Conservative former minister Oliver Letwin, arguing against the meaningful vote amendment, said: "It would have the undoubted effect of providing a massive incentive for our EU counterparts to give us the worst possible agreement.
"I think the situation is worse than (Brexit Secretary David Davis) described, far worse, because this operative sub-clause is deeply deficient as a matter of law."
:: SNP MP Joanna Cherry (Edinburgh South West) said: "On Friday afternoon my constituent...a Lithuanian, attended my surgery in hysterical tears saying the uncertainty caused by this Government and this Parliament is making her feel worse about her personal situation in Britain than she did in Lithuania under the Soviets."
:: Stephen Gethins, the SNP's Europe spokesman, said: "If we pass this today we are passing this Government a blank cheque, a blank cheque on one of the most crucial issues that this Parliament has ever discussed, and one that will have an impact on each and every one of us and each and every one of our constituents."
He later added: "It is the House of Lords, of all places, the House of Lords, that has given us another opportunity today to save the House of Commons' blushes."
:: Conservative former minister Edward Leigh said: "The simple truth is this - deal or no deal, vote or no vote, positive vote or negative vote, this process is irreversible, we're leaving the EU and that's what the people want."
:: Conservative former immigration minister Mark Harper said on the issue of rights for EU nationals living in the UK: "What I'd like us to do as a country is be more generous to those who come here to work, to contribute and to study.
"But I'd like us to be less generous to those who come here to break our laws and violate the welcome and trust we have placed in them.
"I don't want to fetter the hands of ministers in doing that. The amendment as drafted is poorly drafted, doesn't provide that reassurance and I ask the House to reject it."
:: Labour MP Hilary Benn, who chairs the Brexit select committee, said: "I listened also carefully to the language which was used by the secretary of state (for exiting the EU, David Davis). He talked about being able to act without our hands being tied. He talked about being able to pass the Bill without any strings attached.
"I just say to him, we, this House, we are not strings. We are part of our democracy, and we are very attached to that democracy.
"There is a terrible irony in hearing voices of those who in the course of the referendum used as one of their principal arguments that we should vote to leave to restore the sovereignty of Parliament, to then now see their enthusiasm for that democracy disappear in a puff of smoke when the House is asked to put that sovereignty on the statute book."