Demonstrators hold placards in the "Brexit Betrayal Rally" in London, Britain, on Dec. 9, 2018.? (Xinhua/Ray Tang)

LONDON, Dec. 9 (Xinhua) -- The British House of Commons' committee on Exiting the European Union (EU) unanimously agreed in a report its downbeat verdict on Brexit Sunday, saying Prime Minister Theresa May's deal fails to offer sufficient clarity or certainty for the future of the country.

The highly critical report came just 48-hours before the House of Commons decides whether to approve, or as expected, rejects, the Brexit deal May has reached with Brussels.

The committee in its report said: "After 20 months of negotiations, we only know the terms of the UK's departure but not the nature of the future relationship with the EU. The Prime Minister's deal fails to offer sufficient clarity or certainty about the future."

It said the Political Declaration agreed between May and the EU only sets out a series of options, adding that people and businesses will continue to face significant uncertainty about the terms of Britain's trading relationship with the EU after the transitional period ends in December 2020.

"If the government's main priority is to secure UK-EU trade that is as frictionless as possible, it must decide how far it is willing to follow EU rules. This is not a choice the government has so far been willing to make," added the report.

Hilary Benn, chairman of the committee, said in the report: "The Political Declaration... does not give the British people or our businesses the clarity and the certainty they need about our future trading relationship with the EU in five or ten years' time. And with these negotiations having not even having started yet, this could take years to sort out."

Commenting on the so-called backstop position on the border between Northern Ireland and Ireland, the report said activating the backstop would result in immediate barriers to UK-EU trade in goods and services.

By July 2020 if the future relationship between the UK and the EU is not in place, Britain could face the threat of significant economic disruption which would reduce its leverage in the negotiations. If the two sides agree to extend the implementation period, the same problem could surface one or two years later.

MPs will return to Westminster Monday afternoon to start the fourth day of debate on the Brexit withdrawal agreement, ahead of Tuesday when they will vote.