Media playback is unsupported on your device Media caption It costs £26 billion a year to run Northern Ireland, but only £17 billion is being currently raised

NI's health service funding model is unsustainable, according to the health department's top civil servant.

It costs £26 billion a year to run NI but only £17 billion is being raised. The amount needed to maintain the health service goes up each year.

Continuing this model for 20 years would mean spending NI's entire budget on health, warned Richard Pengelly, the department's permanent secretary.

"We can't continue the way we are," he said.

"We have enough money to run a world class health service, but we don't have enough money to run this health service."

Image caption There are currently 11 hospitals in Northern Ireland providing emergency or acute services

"At the moment to run the same service this year as we did last year and next year, it's about 6% increase per annum.

"If we continue on that trajectory, within about 20 years the health service will need virtually all the money that's available to the executive."

Mr Pengelly was speaking to the BBC as part of Spend it Like Stormont which, made by Below the Radar and investigative news website The Detail, is an in-depth look at:

How much it costs to run Northern Ireland

What subsidies do we get from Westminster

How we can balance the books while still running good public services

How different people would make difficult choices about public service spending - and cuts

Northern Ireland is not alone in running on a deficit; the only areas of the UK that have a surplus are London, and England's south-east and eastern regions.

Eleven Northern Ireland hospitals provide emergency, or acute, services - one for every 170,000 people, compared to Wales, for example, which has one for every 230,000 people.

Image caption Richard Pengelly said the Northern Ireland executive's spending 'cannot continue the way it is'

But Mr Pengelly denies the department sees closing hospitals as a solution to the funding problem, preferring to talk about services.

"None of our work will involve taking a hospital and saying: 'Do we need that hospital?'

"It is saying that within that environment, there are a range of services we could offer."

How would you spend it?

Image caption Northern Ireland's health service is allocated with the most money from the budget

With the help of Ulster University's economic policy centre, we have devised a few scenarios on how you might spend Northern Ireland's budget allocation.

Click here to play

"It may mean that members of the public have to travel a little bit further and in some cases a little less.

You can't replicate every service in every location."

Looking after the elderly

Social care for the elderly is another area that will need more money in the future.

"We're not just seeing an increase in the number of older people, we're seeing a reduction in the number of younger people," said Northern Ireland's chief social worker, Sean Holland.

He asks where we are going to get the workforce in the future to provide the taxes to pay for it? And what about enough people to provide the care?

"It is a challenge and that's why we have to have a debate," he said.

"Is it fair to ask a generation that hasn't got access to free university education, that can't buy their own home and don't have jobs for life, and say to them: 'Through your taxes you're going to have to pay for the care of a generation who had all of those benefits?'"

Image caption Education is Northern Ireland's second highest spending department

Education is Northern Ireland's second biggest spending department, and it has experienced budget cuts of 10% in real terms.

Sharon O'Connor, chairwoman of the Education Authority, concedes that our system - which includes state, religious and integrated schools - is both hard to justify and unsustainable.

"It's a by-product of our interesting and complex history," she said.

Image caption Spend it Like Stormont is presented by William Crawley, Tara Mills and economist Neil Gibson

"We have people in society who have preferences for different types of education, so we have a fabric that's quite complex, that many people have strong views about.

"Overall we have a very high standard of education, but we've got to deliver that in a more sustainable way.

That requires changing both the number and the type of schools, she said.

Spend it Like Stormont is on BBC1 Northern Ireland on Wednesday 12 June at 21:00 BST and will be available on iPlayer shortly afterwards.