The NHS is set to be one of the key 2015 election battlegrounds, up there with immigration, Europe, and who can name the most people they met in the park. So this week's spat between the Tories and Labour on the state of the NHS in Wales and England is significant. The Conservatives have this week accused Welsh Labour of running a sub-standard service, helped along by an incendiary investigation into standards of healthcare in Wales run by the Daily Mail. Today at Prime Minister's questions, David Cameron accused Ed Miliband of being “terrified” to discuss his party's "failure" in the country.

Labour disagrees, saying they will happily defend their record in Wales. As one source puts it: “it's an issue we're very happy to debate and [we're] very happy that we'll see it up in lights.”

So, how bad is Labour's record really on the NHS in Wales?

Stand up and be counted

David Cameron's main line of attack at PMQs was his claim that Labour doesn't want the OECD to conduct a comparative investigation into the performance of the NHS in England and Wales. Labour sources have briefed that the Prime Minister is wrong: they are happy to agree to the study, so long as it is not quoted from or pre-released in advance of the election. The Welsh government may be justified in their wariness—Welsh first Minister Carwyn Jones recently called the OECD “the most politicised department in Whitehall,” and said they couldn't trust them with confidential information. That said, one expert who has worked on a major study of the Welsh NHS tells me that the Welsh government were “incredibly anxious and concerned and worried” about the work he was doing. That suggests they may have insecurities about the standards of the Welsh NHS which go beyond poor political relations.

The exodus

Central to the Conservative line of attack are claims that too many Welsh patients are leaving the country to seek treatment in England. Health Secretary Jeremy Hunt has said that for every English patient treated in a Welsh hospital, five Welsh patients were treated in England. According to the LSE's Professor Gwyn Bevan, this doesn't necessarily reflect badly on the performance of the NHS in Wales. Rather, the sparsely populated nature of the Welsh border means that there are few large hospitals there, but there are plenty in England, for example in Liverpool to the north and Bristol to the south. This means it is natural that a large number of Welsh patients will seek treatment in England. As such, the Welsh NHS only has cause for concern if the number of Welsh patients heading over the border is increasing, Bevan argues. According to Labour, the reverse is true: there has been a 10 per cent fall in the number of Welsh patients seeking treatment in England since 2010, they say. Reports of an “exodus” of Welsh patients can't be reliably used to criticise the Welsh health service.

Show me the money

David Cameron today accused Labour of cutting the NHS budget in Wales. Labour sources retorted by briefing that David Cameron had cut the overall Welsh budget, from which NHS funding is drawn, by 10 per cent. Both are right. The Treasury have made a series of cuts to the Welsh budget as part of George Osborne's wider austerity programme, meaning that overall the budget for 2015-16, at £15.1bn, will be 10 per cent lower in real terms than the budget in 2010. At the same time, Bevan explains, the Welsh government has cut the NHS within that budget, because it considered protecting local government to be more of a priority than England and Scotland did. Spending on local government only fell by 4.5 per cent in real terms between 2010 and 2013, compared to 9.5 per cent in England. Spending on the NHS in Wales fell by 4 per cent between 2010 and 2014. In not ring fencing the NHS in Wales, the Welsh government has shown the health service to be less of a priority there than it was in England.