Brexit will be unsustainable and could be undone unless it works for young people, ex-Cabinet minister Justine Greening said.
The former education secretary and prominent Remainer - who left the cabinet in Theresa May's reshuffle after refusing to move jobs - made her first major intervention during a debate on the EU Withdrawal Bill in the Commons on Wednesday.
"I represent a very young constituency here in London," the Putney MP said.
"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."
In response to comments from her former Cabinet colleague, the prime minister's spokesperson said she was "determined to deliver a Brexit that works for everyone".
Ms Greening was speaking in response to former chancellor Ken Clarke, who said future generations risk being made less prosperous if economic barriers are put up between the UK and EU post-Brexit.
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.