We are less than a week into the election campaign and already there has been a plea not to use the NHS as a "political weapon".

Chris Hopson, the chief executive of NHS Providers - the umbrella body for hospital, ambulance, mental health and community care trusts in England - called for a "proper, mature, evidence-based" debate from politicians on the future of the health service.

He is likely to be disappointed.

Time and again that same refrain is repeated by staff on the ground weary at the way missed waiting list targets or staff shortages are used to score points against the party of government.

"Let's not resort to the cheap political slogans and skimming across the top which is what we've seen over the last four or five elections," Mr Hopson said, adding that "it becomes counter-productive when the NHS is used as a political weapon".

The problem is that when the NHS accounts for the largest share of public spending - including more than £14 billion in Scotland - that makes it inherently political.

Taxpayers have the right to know what sort of return they are getting on their investment, and to judge in whose hands the service might be safest.

Notably, the NHS is run by the SNP in Scotland, the Conservatives in England and Labour in Wales.

This makes it fertile territory for 'whatabootery' as SNP opponents can always find something being done better elsewhere (Wales were first to introduce opt-out organ donation, while NHS England already offers stroke patients thrombectomy) - while SNP loyalists can point to those areas where Scotland's NHS is outperforming England's (Scotland has shorter A&E waiting times on average, for example, and the highest share of GPs per head in the UK - 76.2 per 100,000 compared to a low of 58.1 per 100,000 in England).

Health is devolved, of course, but it is up to whoever takes the helm at Westminster to determine if or how we 'Brexit'.

From the medical Royal Colleges to trade unions including the BMA or cancer charities, there is little appetite for any sort of Brexit.

They fear the impact on staffing (Scotland's health and care services, particularly in rural areas, are highly reliant on EU workers), the cost of medicines and a reliable supply of drugs that cannot be stockpiled, such as radioisotopes for cancer treatment.

At one end of the spectrum the Tories have vowed to 'get Brexit done', while the LibDems promise to abandon an EU exit altogether. The SNP want an indyref2 so that Scotland can chart its own path as an EU member state, while Labour would hand the final say back to the public with a second referendum.

It will also be up to the next Government to set the budget for health.

Jeremy Corbyn has said he will end austerity in the NHS via a "proper funding settlement", with Scottish leader Richard Leonard warning during a campaign visit to Monklands hospital that a Tory Brexit would leave the NHS open to "private interests based in America".

"People are rightly concerned about what that would do to access to drugs companies," he said.

However, Boris Johnson is also expected to outline billions of pounds of extra investment in the NHS, in addition to £2.7bn for six new hospitals in England.

How much Scotland has to spend on health is largely determined by our share of public expenditure as set by the Barnett formula.

Increased public spending in England would translate into extra funds for Scotland, but it would be up to the SNP-led Scottish Government how to invest it.

Scottish Conservative leader Jackson Carlaw used his latest campaign outing to attack the SNP's record in this area.

He said: “The real scandal is the SNP failure to pass on all the additional monies it has received in recent years and to increase NHS spending at the same high level as the rest of the UK."

A 2017 report by Oxford University economist, Professor Jim Gallagher, said the NHS in Scotland would have received an extra £750 million over the previous decade if the Scottish Government had passed on all the so-called “Barnett consequentials” of health spending from the UK Government.

Treasury figures also show that health spending in England increased by 17.6% between 2012-13 and 2017-18, but by only 13.1% in Scotland over the same time period.

The Scottish Government argues that more is spent per head on health in Scotland than anywhere else in the UK (£2,353 in Scotland in 2017/18, compared to £2,168 in England).

This is all smoke and mirrors, however.

Forget meaningless claims of "record spending": the UK has consistently invested less than 10% of GDP on health compared an average of 12.6% across OECD countries.

Consequently, the UK also has some of the lowest rates of doctors and nurses in the OECD: there are just 2.82 doctors per 1000 population compared to 5.13 in Austria, and 7.86 nurses per 1000 population compared to 17.73 in Norway.

Transforming the fortunes of the NHS means serious real-terms investment in hospitals, GPs, and social care - and a government with the guts to do it.