Jo Swinson warned she will face challengers for Lib Dem leadership

Liberal Democrat leader Sir Vince Cable could step down before the end of the year – but the favourite to succeed him, deputy leader Jo Swinson, should expect a challenge for the top job, senior party sources have said.

Jo Swinson's appointment as deputy leader of the Lib Dems was uncontested - but she has been warned landing the top job will be tougher. Picture: PA

And the East Dunbartonshire MP could find herself up against a “celebrity” candidate under new rules set to be approved next month that will open up the party’s leadership to non-members.

Insiders said that Swinson had broad support for a leadership bid, but insist there has to be a full contest after Cable won the role unopposed following the 2017 general election.

Sources close to Cable (above), who is 75, have signalled that he does not intend to lead the party into another election, unless a snap vote is called in the near future.

Rather than a timetable for his departure, he has set a series of objectives, including passing reforms to turn the Lib Dems into a “movement for moderates”, and campaigning to stop Brexit through a second EU referendum.

The reforms are set to be debated and passed next month, with the UK leaving the EU shortly thereafter. Meanwhile, there has been speculation that Prime Minister Theresa May could call a snap general election in the summer, timed to coincide with local elections in England on 2 May.

“Vince set himself some clear goals when he became leader,” one Lib Dem MP said, adding that it was “entirely possible they could be met by the end of the year”.

Swinson is understood to still be considering whether she wants to run for the party leadership, but she is popular among party members and would be expected to win the backing of most of the Lib Dem parliamentary group, including her three fellow Scottish MPs.

A second Lib Dem MP said: “I really hope Jo runs, and if she does, she’ll win – but the party membership doesn’t want a coronation. There has to be a challenge.

“The Tories had a coronation in 2016, and look what happened there. It just wouldn’t look good.”

The first source said demands for a contested leadership election were “a correct reading of opinion in the party”.

Potential challengers inside the parliamentary group could include the Oxford and Abingdon West MP Layla Moran, the first person of Palestinian origin to sit in the Commons, and former energy minister Ed Davey.

But Cable’s bid to turn the Lib Dems into a mass-movement similar to Emmanuel Macron’s En Marche party in France could attract some well-known anti-Brexit names to the contest.