Brexit will “not be sustainable” if it does not work for young people, Justine Greening has said.

The Conservative former cabinet minister added that future generations of MPs could seek to “improve or undo” what the current cohort implements.

Ms Greening’s intervention came just days after she left the Cabinet after declining to move from education secretary to take control of the work and pensions brief during Theresa May’s reshuffle.

Former chancellor Ken Clarke also claimed future generations risk being made less prosperous if economic barriers are put up between the UK and EU post-Brexit.

Tory grandee Mr Clarke added the UK would inevitably take an “economic blow” in such a scenario, which could have a knock-on effect.

The opening lines of the European Union (Withdrawal) Bill
The opening lines of the European Union (Withdrawal) Bill (PA)

MPs are close to concluding debate over possible amendments to the European Union (Withdrawal) Bill, which transfers European law into UK law.

The Bill is expected to receive a third reading on Wednesday before appearing before the House of Lords by the end of January, where it is expected to receive a rocky ride as it continues its parliamentary journey.

Speaking in the Commons, Ms Greening said: “I represent a very young constituency here in London.

“The bottom line is that looking ahead if Brexit doesn’t work for young people in our country, in the end it will not be sustainable.

“When they take their place here they will seek to improve or undo what we’ve done and make it work for them.

“So we do absolutely have a duty in this House to look ahead and ensure that whatever we get is sustainable and works for them.”

Conservative MP Ken Clarke
Conservative MP Ken Clarke (PA Archive)

Earlier Mr Clarke, also speaking at report stage, said: “On whatever basis we come out, there are bound to be adverse effects on the British economy if we create new barriers between ourselves and the biggest free market in the world.

“There is no other government, I think, that would remotely contemplate moving out of such a completely open and free market and actually deliberately raise barriers by way of tariffs, customs processes or the regulatory divergences between themselves and such a hugely valuable market.

“Of course it’s particularly valuable to us because it’s not only a huge market, it’s on our doorstep and we have played a very major part in creating this totally open trade.

“If in fact we proceed to a deal in which we withdraw then we’ll find ourselves – to some degree or another – inevitably taking an economic blow and probably making future generations less prosperous than they would otherwise have been.”

Mr Clarke added it is a “great pity” the Commons has not received the necessary information to make a “really informed judgment”.

Asked about Ms Greening’s comment, Theresa May’s official spokesman said: “The Prime Minister is clear that she is determined to deliver a Brexit which works for all sections of society. Of course that would include young people.”