Mr Rennie says the Conservatives are not proposing one new tax on rich people, unlike the Lib Dems.

Mr Murphy says Labour doesn't want to tax working class people. He says if you earn more than £150,000, your taxes will go up.

Ms Davidson said the £12bn will include freezing benefits for two years and adds that other savings will come from getting more people into jobs.

Ms Sturgeon says the Conservatives want £30bn more cuts after the election, including £12bn in welfare.

Morv tweets, external: #leadersdebate let's talk about quality of spending NOT quantity!

Dianne Maureen Smart tweets, external: #leadersdebate Alex is not leader of the SNP....

Alan tweets, external: Anyone else watching for a fake tache? #leadersdebate

What is the Barnett Formula?

• It's a system of grants which dictates the level of public spending in Scotland, Wales and Northern Ireland.

• Under it, extra funding - or cuts - from Westminster are allocated according to the population size of each nation and which powers are devolved to them.

• When the UK government increases or decreases funding for departments such as health and education in England, the Barnett formula is used to decide how much devolved governments will receive.

• The formula is named after its inventor, the former Labour Chief Secretary to the Treasury Joel Barnett, who devised it in the late 1970s.

Mr Coburn says UKIP wants to gradually wean Scotland off the Barnett funding formula which pays for Scotland's budget, in favour of the nation raising its own taxes.

Patrick Harvie disagrees with Mr Coburn. He says the next generation of industry to replace "outgoing" fossil fuel industries needs investment.

Mr Coburn gets in a cheeky dig at the SNP, describing Alex Salmond as the party's leader.

David Coburn says the SNP wants to spend money it doesn't have. He says governments don't create jobs - businesses do. He adds that more poorer people need to be taken out of having to pay tax.

Willie Rennie says the Tories want to "balance the books on the backs of the poor", while Labour and the SNP wants to borrow too much. He says the country needs to "stay the course".

Ruth Davidson says it's not responsible to "pass debts on to our children". She says the UK is spending a huge amount of money on servicing debt - a bit like only paying of the interest on large credit card debts.

Fuad A. tweets, external: #LeadersDebate: Jim Murphy - "we can grow and invest in our people". Jim, we are human, not fruit trees.

Nicola Sturgeon says this approach has been holding back the economy and have hit the 10% poorest people in communities the worst. She says there should be modest spending increases of 0.5% in the next parliament to allow more investment while cutting the spending deficit at the same time.

Mr Murphy says you don't have to cut your way out of austerity.

Jim Murphy says it's time to end the "failed austerity experiment" put forward by the Tories. He says that will end under Labour.

Paul Daly tweets: Here we go again! I'm looking forward to hearing from @patrickharvie & hearing the full Scottish political spectrum tonight! #LeadersDebate

The debate is taking place from Elphinstone Hall in Aberdeen and is being broadcast on BBC One Scotland at 21:00 (two minutes' time).

To follow the debate on social media use #leadersdebate, external