Theresa May will not back down in her battle with the House of Lords over Parliament getting a veto on the final Brexit deal despite a Tory rebellion threatening a defeat for the Government, the Conservative Party chairman has said.

Sir Patrick McLoughlin insisted the Brexit Bill should go through the Lords without peers making any changes to it.

He spoke after Tory grandee Lord Heseltine vowed to rebel against the Prime Minister to back an opposition bid to ensure a meaningful vote on the final deal she achieves in Brexit negotiations.

A Labour Lords source has said the party "would be likely to win handsomely" in a vote on the issue in the coming weeks, and in a bid to guarantee rights of EU nationals already in the UK, if the Government does not come forward with concessions.

But Sir Patrick insisted the European Union (Notification of Withdrawal) Bill, which will give Mrs May the power to begin exit negotiations under Article 50, should go through the Lords without changes.

He told BBC One's Andrew Marr Show: "We will want to see how the Bill evolves once it's out of the House of Lords.

"But look, the Bill got an overwhelming majority, one of the biggest majorities a Bill has got on its third reading in the House of Commons and it's gone to the House of Lords.

"The Prime Minister has said that there will be a vote once the negotiations are concluded, the Prime Minister won't conclude the negotiations if she thinks she's got a bad deal."

Asked if the Government was ready for a "fight" with peers, he said: "We'll see whether we're going to have a fight or not.

"The Bill should go through as it has come from the House of Commons, the elected House of Commons.

"We can't now start second-guessing the referendum.

"The Prime Minister will not come back to the House of Commons with a deal that she cannot recommend, so that is what we have got to do. We've got to give the Prime Minister as much flexibility in the negotiations over those next two years, not giving her a backstop to other issues."

A vote on whether Parliament should have a meaningful say on the final deal is not expected during the Bill's committee stage next week, but is more likely during report stage on March 7, the Labour Lords source said.

The rights of EU nationals and the effect of Brexit on the Good Friday Agreement and Northern Ireland peace process could also be flashpoints during committee, the source added.

Lord Heseltine said Labour, Liberal Democrat and rebellious Tory colleagues will back an amendment on a final vote in order to uphold the Supreme Court's ruling that MPs and peers have ultimate authority.

Writing in The Mail On Sunday, he said: "In the end, the outcome of Brexit will have to be confirmed by Parliament.

"It will also have to pass in 27 national European parliaments, several sub-national parliaments and the European Parliament.

"It was perhaps unwise for our Government to suppose that our Parliament should be excluded where all others were included.

"Very sensibly, after the Supreme Court interpreted the law, that position was reversed and Parliament was restored to its rightful constitutional role as the ultimate authority.

"I will vote in the House of Lords to ensure that position is legally intact.

"This is not a confrontation with the Government which has already made such a commitment.

"It is, put simply, a decision to ensure that the Commons has the chance to define its role in the exercise of its authority over what most people regard as the defining issue of our time."

If the Bill is amended, a period of parliamentary "ping pong" may follow, with MPs asked to vote on changes made in the Lords.

But Mrs May expects to be able to stick to her timetable of beginning talks with Brussels by April.

Home Secretary Amber Rudd said there was no possibility of Mrs May agreeing to any amendments to the Bill.

She told ITV's Peston on Sunday: "No I don't think there is any possibility and I don't think there should be. This is a process Bill.

"It's just about beginning the process for the two years that we're going to need the time in order to prepare for leaving. Then within that, there'll be the opportunities to debate and discuss."