Mr Rennie says his party is prepared to put up air passenger duty, meaning frequent flyers will pay the most.

"Just pussyfooting around on this isn't actually going to stop climate change."

Nicola Sturgeon says the Scottish government has set the most challenging climate change targets in the world.

The first minister says 75% of Scotland's electricity comes from renewables and she says fossil fuel use must be reduced.

She cites her government's U-turn on air passenger duty.

Fiona McQuin asks how the leaders can convince her that they are strong enough to make brave, difficult and potentially economically unpopular decisions in order to combat climate change.

Jackson Carlaw and Richard Leonard clash over austerity and spending plans and Nicola Sturgeon accuses Mr Calaw of "being completely out of touch".

He hits back saying the SNP said they would not put up taxes in its 2017 manifesto and did just that straight after the election.

Image source, Alan Peebles

If we stop Brexit there would be an immediate Remain bonus of £50bn, says Willie Rennie.

He says the IFS have said the Lib Dem proposals are "radical and prudent" and he argues they are costed.

The Resolution Foundation has said the proposals are progressive, even more so than Labour, argues the Scottish Lib Dem leader.

I did not come into politics to impose austerity, says Jackson Carlaw, but the huge financial crisis ten years ago meant cuts were needed to ensure millions of people in this country were not out of work.

She adds that now as we come out of austerity, we can start to "invest sustainably and sensibly in our public services".

We would have millions of people unemployed if the decisions were not made by the UK government, he goes on to say

Nicola Sturgeon says she would like to see progressive taxation and more reasonable and responsible borrowing.

The first minister says she does not think Labour's figures are entirely credible and adds all the other parties want to renew trident at a cost of £200bn, whereas she would like to see the cash invested in health and education instead.

Mr Leonard says in order to boost public services, the burden of taxation must be put on companies and through capital gains tax.

We are the only party setting out in full view how we will raise the money to turn this country around, he argues.

Danielle Gibson says parties are demanding an end to austerity and promising to spend big on things like the NHS, tackling homelessness, social housing and infrastructure, which she says are all good ideas.

It's a force for good as long as it is properly moderated, replies Jackson Carlaw.

Ms Sturgeon thinks unregulated capitalism is a force for bad and calls for more regulation and state ownership where necessary.

It can be a force for good alongside progressive politics, suggests Mr Rennie.

Mr Leonard says he is broadly in favour of socialism and says a mixture of public ownership and private enterprise is best.

A second quick fire question

• Mr Leonard says prisons are already overcrowded so he is not sure locking up politicians is the right thing to do, adding it should perhaps be a civil crime.
• Mr Carlaw says no, but it's a resignation matter.
• It is not something politicians should do regardless of whether it is an offence, Ms Sturgeon argues, before criticising Boris Johnson for lying.
• Mr Rennie agrees with the first minister about Boris Johnson.

This is a quickfire question from an audience member watching online.

Richard Leonard says: "We will not enter into any deals, pacts or coalition arrangements."

The people have the choice to elect a Labour government he says.

The choice is a Boris Johnson or a Jeremy Corbyn government, the Scottish Labour leader says adding he hopes people will vote for his party.

BBC host Sarah Smith asks if Ms Sturgeon would look to do a deal with Labour and the Lib Dems to keep the Conservatives out of government.

She replies that she would hope a progressive alliance could be formed to keep the Conservatives out.

Mr Rennie says both Boris Johnson and Jeremy Corbyn are unfit to be prime minister so the Lib Dems will not do any deal that puts either in power.