Scottish Labour leader Richard Leonard has said unionist is not a term he would use to describe himself as he defended his party's indyref2 position.

Speaking in an election special on STV's Scotland Tonight, he said he was opposed to a second independence referendum but would not block one if there was a "swell of support" for a vote in Scotland.

The party leader is the first of six politicians to be quizzed on the programme by STV's political editor Colin Mackay ahead of the December 12 general election.

In a wide-ranging interview, Leonard also revealed he is a long-standing member of the Campaign for Nuclear Disarmament (CND) - despite Scottish Labour's election manifesto supporting the renewal of Trident.

'I've been a member of the Campaign for Nuclear Disarmament for more years than I care to remember.'

Scottish Labour leader Richard Leonard

He insisted he was "in charge" of Labour's election campaign north of the border but said he would not consider resigning if the party loses Scottish seats.

The Scottish Labour leader was also unable to produce a figure for how much a key manifesto pledge to bring all PFI contracts back into the public sector would cost in Scotland.

With a 2017 manifesto which stated opposition to a second independence referendum, Leonard was asked if his party's new stance against a vote in the "early years" of a Labour government had watered down its commitment to the union.

The Scottish Labour leader insisted: "We are absolutely opposed to a separate Scottish state.

"We are therefore opposed to the holding of a second independence referendum."

But he added that if "at some future point" there was "a swell of support" in Scotland for another independence ballot, Labour would not block it indefinitely.

Asked if a pro-independence majority in the 2021 Holyrood election would count as proof of such support, Leonard answered: "I'm leading the Scottish Labour party into those elections to win those elections.

"So I'm not going to sit here, all the months out from that election, ceding defeat to other parties."

Pressed again on if there could be a referendum in 2021 or shortly after, he said: "I don't envisage that at all."

On whether he would call himself a unionist, Leonard said: "I consider myself to be a socialist and democrat.

"(Unionist) is not a description I would pin on myself.

"I would consider myself to be an internationalist, somebody who is in favour of working cooperatively and collaboratively, working across this shared island.

"I'm somebody who doesn't want to see boundaries and national borders going up, I want to see boundaries and national borders coming down."

Scottish Labour's manifesto echoes that of the UK party's in supporting the renewal of Trident nuclear weapons.

But Scottish party members officially voted to oppose Trident renewal back in 2015.

Asked if he had now given up on that, Leonard replied: "I haven't given up on it all, in fact, I've been a member of the Campaign for Nuclear Disarmament for more years than I care to remember."

But he said, as defence was a reserved matter, he would "abide by the democratic decision" of the UK Labour party to retain the nuclear deterrent.

Leonard denied the Scottish party had been "railroaded" by the UK party into putting Trident support in its manifesto - despite Scottish Labour vowing to take a pro-remain stance in any future Brexit vote, in contrast to UK Labour.

Asked if he was running the Labour campaign in Scotland, he answered: "Yes, I'm in charge of the campaign."

With a recent poll putting Labour on 20% in Scotland - raising the prospect of the party losing all but one of its seven Scottish seats - Leonard denied such a result would cause him to consider quitting.

The Scottish Labour leader said: "This election is not about me and my position. This election is about how we change the country.

"It's about whether we have a decade of austerity or a decade of investment."

Pressed on how much it would cost in Scotland to bring all PFI contracts back into the public sector, he told Scotland Tonight: "We will look at the figures when we get into government.

"The truth of the matter is there is no certainty about the precise costings."

You can watch the full interview with Richard Leonard on Scotland Tonight at 10.40pm on Monday.

It is the first in a series of election interviews with senior party figures to be broadcast in the coming days.

STV will also host a general election debate featuring four of the Scottish party leaders on Tuesday, December 3.