Scrapping Britain’s first-past-the-post electoral system would be a precondition for the Liberal Democrats considering a future coalition with Labour, a contender to lead the party has warned. Layla Moran, who is vying for the job alongside acting party leader Ed Davey, said that she was interested in building significant levels of cooperation with Labour before the next election. She even suggested the parties could build a joint campaigning force where it benefited them. In an interview with the Observer, the Oxford West and Abingdon MP said she was best placed to overhaul her party’s relationship with Labour. Successive Lib Dem leaders have ruled out coalitions with Labour or the Tories since the party’s electoral collapse following its coalition with the Conservatives under Nick Clegg, but Moran said she would not rule out such a deal with Keir Starmer. However, she suggested ending first past the post would be a prerequisite. “I’ve absolutely ruled out a coalition with the Tories,” she said. “I would never say never [to a coalition with Labour], especially with a more centrist progressive Labour leader, as we’ve seen under Keir. We’ve still got a long way to go and I think Labour still has to revamp their own policy platform. I think top of the list of something I’d be looking for is electoral reform. Without it, actually, it would end up hurting the party potentially to do anything. So without seeing the small print, it’s hard to say one way or the other, but it’s not ruled out.” She called on activists within the two parties to consider forming a “huge campaigning force” to help each other at the next election. She said she wanted a “Paddy plus” arrangement with Labour, in reference to the close relationship between former Lib Dem leader Paddy Ashdown and Tony Blair before the 1997 election. “We need to be really smart about it,” she said. “I would like to get to the point where at the very least, in those seats where we stand a chance of defeating the Tories, [activists] aren’t fighting each other, because that just defeats the purpose. But even better, if we can inspire a progressive movement of activists to take those seats off Boris Johnson’s Tories, that’s where I’d like to get to. ‘Paddy plus’ is kind of what we’re aiming for, but it’s not a pact and it’s not anything formal.” Voting to decide who will replace Jo Swinson, who lost her seat in the 2019 election, begins this week. Moran’s manifesto, launched this week, includes support for a universal basic income. However, she rejected the idea that the Lib Dems would be to the left of Labour under her leadership. She said that unlike her rival Davey, who was a minister in the coalition government, she was best placed to build a constructive relationship with Starmer and Labour. “That coalition hangover means that the vitriol between the parties is really palpable. I would love to get to the point where that heat was taken out of the relationship between Labour and the Lib Dems, because that would also help actually achieve something that’s greater than all of this stuff, which is frankly tactical – which is a kinder, gentler politics in our country that is less divisive and generally more respectful.” She said the past decade for the party had “clearly been disastrous”, attacking the party’s support for revoking Brexit. She ruled out backing rejoining the EU for at least five years. “We have to accept that public opinion just isn’t there yet. There’s a battle to be won in the hearts of people first. “Let’s show people why, had we stayed, it would have been in our interests … by making the positive case for why we should have an ever closer trading relationship, why we want to maintain our British-EU standards that we helped to create.”