LONDON - British Prime Minister Theresa May said on Sunday that a failure to support her Brexit deal will be catastrophic for Britain.

In a strongly worded plea to politicians, May described the vote due to be taken in the House of Commons on Tuesday as the biggest and most important decision MPs will be taking in a generation.

Writing in the Sunday Express newspaper, May told the people of Britain: "You have delivered your instructions. Now it is our turn to deliver for you. We cannot, and must not, let you down."

Saying a rejection of the Brexit deal would be a catastrophic and unforgivable breach of trust, May urged the parliament to "forget the games and do what is right for our country."

"If parliament does not come together and back this deal in our national interest we risk leaving with no deal, with all the uncertainty for jobs and security that will bring," she said.

MPs will gather at Westminster Monday to resume their marathon debate on the Brexit bill ahead of the vote early Tuesday evening.