LONDON, Oct. 22 (Xinhua) -- British Prime Minister Theresa May said Monday that Britain and the European Union (EU) have agreed to 95 percent of a post-Brexit relationship agreement.

Addressing MPs in the House of Commons, May said people are understandably worried that Britain could get stuck in a backstop arrangement designed to be temporary on the issues still remaining to be resolved.

Outlining steps still needed to be taken, May said Britain must be able to leave the EU at will, not be locked into any arrangement "against our will".

The major remaining unresolved issue is the future of the border between Northern Ireland and the Republic of Ireland.

"There is one real sticking point left and a considerable one which is how to guarantee no return to a hard border in Ireland," said May.

May has ruled out any solution that would keep Northern Ireland having to follow EU rules, or a border along the Irish Sea that would see Northern Ireland cut off from the rest of Britain.

May said Britain has proposed a legally binding joint UK-EU joint customs territory to help break impasse.

She told MPs that in a substantial shift in their position the EU is now actively working with Britain on the proposal.

May said she has not committed Britain to extending the Implementation Period, adding: "I do not want to extend the Implementation Period and I do not believe that extending it will be necessary."

"By far the best outcome for the UK, for Ireland and for the EU -- is that our future relationship is agreed and in place by 1st January 2021," she added.

Vince Cable, leader of the minority Liberal Democrats asked May about reports that the government is carrying out contingency planning for a second referendum.

The prime minister replied: "No, that is not correct. The government does not support a second referendum."

Jeremy Corbyn, leader of the main opposition Labor Party told MPs that May had traveled last week to the meeting in Brussels of the 27 leaders of EU member states "to beg for an extension" of the transition period due to end in December 2020.

As May shook her head to deny the claim, Corbyn said her Conservative government is "terminally incompetent, hamstring by its own division".

May told MPs that as she travelled around the county people who voted either leave or remain had told her "to get on with it" and leave the EU.