JO Swinson has left the door open to challenging for the Liberal Democrat leadership once Sir Vince Cable steps down.

The current deputy leader, 38, also made clear the party had to change to attract new voters but that there was no need for a new centrist party as it already existed in the Lib Dems.

Appearing on Sky News' Sophy Ridge On Sunday, the MP for East Dunbartonshire, who has hitherto suggested she is presently not interested in the leadership role – she recently gave birth to her second child - was asked if she would consider running for it.

She replied: "There's no vacancy at the moment. Vince has set out the things that he wants to do before he stands down." But then she added: "At the time that Vince does stand down, then absolutely I'll take a view at that point."

Ms Swinson, a form Business Minister in the Lib-Con Coalition government, also dismissed talk of a new centrist party as "fodder for Sunday newspapers" and said that she had not been approached over the formation of one.

She explained: "We've got the ingredients to be able to challenge the other parties, we've got the infrastructure of parties right across the country in terms of local associations, candidates, the whole idea of a centrist party gets talked about endlessly but doesn't really get off the ground.

"You don't need to set up a new party because the Liberal Democrats are here but we recognise that we have to change in order to make it easier for people that perhaps haven't looked at us before to look again at the Lib Dems."

The proposed changes include setting up a registered supporters' scheme and opening up the leadership to candidates who are not MPs.

Ms Swinson also told how she hoped the Labour Party would shift its position on a second EU referendum after an intervention from London Mayor Sadiq Khan.

Writing in the Observer, he insisted that the public should be given the chance to reject a Brexit deal, which would "be bad for the economy, jobs and the NHS".

Welcoming his comments, the Scot added: "It shows that momentum is building to have a people's vote on the deal."

Meanwhile, Sir Vince, 75, rejected claims he was running out of steam as the Lib Dem leader as he again refused to set a firm resignation date; most Westminster-watchers believe it will be sometime next year.

The Twickenham MP told BBC 1's Andrew Marr Show: "I'm not running out of road, there's a lot of road ahead."

Asked if he would still be party leader by the end of next year, Sir Vince said: "That's uncertain. I have a series of tasks to do. I'm going to do them. I'm not setting a time horizon. It would be foolish to do so with so much uncertainty flying around."

Pressed on being at the helm at the time of the next slated General Election in 2022, he said: "2022 is a long time off; I think it's improbable, actually, that I will be leading us then."