A landmark law giving Theresa May the power to start Britain's divorce from the European Union faces its final Parliamentary hurdle later.

MPs are likely to overturn changes to the Brexit Bill made by peers when it returns to the Commons on Monday afternoon.

Backing by the Lords when the legislation is sent to the upper chamber in the evening would allow the Prime Minister to fire the starting gun on exit talks as early as Tuesday.

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Brexit Secretary David Davis called on Parliament to give Mrs May a clear run at the two-year negotiation process that will begin when Article 50 is triggered.

"Please don't tie the Prime Minister's hands in the process of doing that for things which we expect to attain anyway," he told BBC One's The Andrew Marr Show.

"What we can't have is either House of Parliament reversing the decision of the British people."

Up to 10 Tory MPs are reportedly considering opposing the Government or abstaining in the vote but a rebellion would need to reach higher numbers to derail the process.

Labour sources warned there was a 20% chance of peers sending the Bill back to the Commons again if their amendments are dismissed out of hand, in another round of so-called Parliamentary ping-pong.

The House of Lords changed the European Union (Notification of Withdrawal) Bill to introduce a ''meaningful'' parliamentary vote on the final deal with Brussels and guarantees on protections for EU nationals living in Britain.

Mrs May will go before MPs on Tuesday to update them on talks she had with other EU leaders at a European Council meeting last week.

Speculation is mounting she will use the opportunity to formally announce she is starting the exit process, although there is still plenty of time before the self-imposed deadline of the end of March.

International Trade Secretary Liam Fox refused to be drawn on the timing, insisting only it would be within the next three weeks.

The Cabinet minister admitted crashing out of the EU without a Brexit deal would be "bad" for Britain and said it was "not in anybody's interest" for the talks to end in failure.

But Foreign Secretary Boris Johnson insisted Britain "would be perfectly okay" if no agreement was reached and it would not be "as apocalyptic as some people like to pretend".

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Former minister Anna Soubry, meanwhile, claimed talks could collapse within six months and leave Britain falling off a cliff-edge.

Quitting without a deal and moving to World Trade Organisation (WTO) rules would put UK trade with the EU on less generous terms than any other country in the G20, according to House of Commons Library research.

All of the leading nations have some form of preferential agreement with Brussels, ranging from full free trade agreements to equivalence deals.

Labour's Pat McFadden, a supporter of the Open Britain campaign to keep strong ties with the EU who commissioned the research, warned threatening to walk away without a deal was "dangerous".

"The Government is flirting, as a negotiating tactic, with an option that poses huge dangers to UK industry, services and agriculture," he said.

"This is why it is vital for Parliament to have a meaningful say in the negotiations to come, and to have a say on both a Free Trade Agreement and what should happen in the event of no deal being agreed."

Former education secretary Nicky Morgan indicated that potential Tory rebels would back down if the Government can give new assurances over a vote on the outcome of negotiations in Monday's debate

Mrs Morgan said having a vote on the endgame was "not about making sure that Brexit doesn't happen" and warned Theresa May she would face Tory disunity unless she gives in to the demands.

"I think if the Prime Minister wants a united party then this is a simple reassurance that can be given by ministers at the despatch box that will have the effect, as I say, of my and my colleagues supporting the Government in this," she told the BBC Radio 4 Today programme.

She signalled she would back the Government on EU nationals.

Former chancellor Lord Darling of Roulanish said peers should back down if their amendments are overturned by MPs but backed Mrs Morgan's stance on a meaningful vote.

The Labour peer told Today: "The job of the Lords is to ask the Commons to think again.

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"The Commons has got to be supreme.

"I was 27 years a member of the House of Commons, I feel very strongly about that, the Lords is there to revise but at the end of the day the House of Commons is a democratically elected body.

"I don't want Brexit, I think it's bad, I think we'll regret it, but that's the way it is."