THERESA May has raised the prospect of a longer Brexit transition timetable than was previously suggested.

The Prime Minister said the implementation period will end “well before” 2022 when she addressed MPs yesterday after facing criticism over the proposal designed to help end the deadlock in talks with the European Union.

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Her suggestion came after Brexit Secretary Dominic Raab said it could last three months.

In a Commons statement following last week’s EU summit in Brussels, she stressed that in any circumstances the transition – originally due to end at the end of 2020 – would have to be over “well before” the end of the parliament expected in June 2022.

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“There are some limited circumstances in which it could be argued that an extension to the implementation period might be preferable, if we were certain it was only for a short time,” she said.

“For example, a short extension to the implementation period would mean only one set of changes for businesses – at the point we move to the future relationship. But in any such scenario we would have to be out of this implementation period well before the end of this parliament.”

May faced a furious response from some Tory MPs after it emerged the possibility of an extension to the transition period had been discussed by EU leaders in Brussels. It prompted accusations the UK could be forced to pay billions into EU coffers for months – or even years – to come after it has left the bloc and also that it would remain in the Common Fisheries Policy for considerably longer than promised during the 2016 referendum.

Scottish Tory MPs have promised to vote against any deal which extended the implementation timetable.

Labour leader Jeremy Corbyn told the Commons the latest Government strategy to extend the transition period was a “shambolic failure”. He said: “This Government is terminally incompetent, hamstrung by its own divisions ... Their Brexit negotiations have been a litany of missed deadlines, shambolic failure and now they’re begging for extra time. Instead of taking back control they’re giving away our say and paying for the privilege. What an utter shambles.”

Corbyn told MPs a customs union would provide a “simple solution” to the border issue, adding: “It’s a solution that not only benefits Northern Ireland but would help safeguard skilled jobs in every region and nation of Britain. No hard border in Ireland and no hard border down the Irish Sea, and good jobs for every region and nation.”

The SNP’s Westminster leader Ian Blackford urged May not to sideline Scotland and called for Holyrood to have a say in any Brexit deal. “Time and time again Scotland’s interests have been side-lined by the UK Government.”

He continued: “Today I’ve made it clear to the Prime Minister our Parliament – the Scottish Parliament – must have a say. Twice now I have warned the Prime Minister – any deal that falls short of staying in the single market and the Customs Union will not get through Parliament.”