Wigan MP Lisa Nandy has told broadcasters Brexit delays which means Britain has to elect politicians to the European Parliament will be deeply unpopular.
Ms Nandy told Sky News' All Out Politics programme that a delay to departing the EU which is so long Britain would have to have serving MEPs in Brussels and Strasbourg would create a backlash from voters in the borough and further afield.
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She was speaking on Friday morning as parliament prepared to consider voting for the withdrawal agreement prime minister Theresa May negotiated with the EU without the political declaration suggesting the outline of future trade talks.
Ms Nandy said: "European elections are something that is looming quite large in a lot of people's minds. I think it would be a very difficult prospect to go back to the country and say to people now we have to elect MEPs to a parliament we promised we would leave three months earlier.
"It certainly wouldn't go down well back in Wigan."
Ms Nandy also offered little comfort to those already sick and tired of Brexit, saying the longest and toughest negotations about Britain's future relationship with the EU have not even got under way yet.
Ms Nandy had backed an amendment which would have approved the withdrawal agreement as long as parliament had a much greater say on the future relationship.
However, she told broadcasters on Friday morning it was "unlikely" she or many other Labour MPs would back the PM in the vote later that day.
She said an agreement that would be successful in the House of Commons should have "the political declaration that goes alongside it, with a role for parliament and a vote on what comes next".
She added: "Only then - I hate to say it - will we get to the real negotiations, which haven't even started yet."
Ms Nandy also explained why she thought another public referendum on Brexit was a bad idea.
She said: "I've never been opposed to asking people what they think about the future relationship but there are better ways to do that which are less divisive and don't perpetuate this horrendous divide we have.
"We need to reset this, in the country as well as in parliament, so we can look for common ground as well as the things that divide us."
She said one way of doing this would be the proposal for citizens' assemblies she has previously floated along with fellow Labour MP Stella Creasy.