Prime Minister David Cameron stuck the knife into Labour after saying its handling of Wales' NHS had turned the Welsh border into a dividing "line of life and death".
A war of words has erupted between the two rival governments in London and Cardiff Bay in recent weeks over their differing policies on health.
Carwyn Jones' administration in the Welsh Assembly has come under repeated criticism from rivals amid increasing waiting time lists and claims of underfunding.
And Mr Cameron sought to turn up the heat further during his speech at the Welsh Conservatives' conference in Llangollen yesterday.
While talking up his party's record on the economy and how the upcoming Nato summit would boost Wales, he was quick to put down Labour.
He said: "Doctors and nurses are being woefully let down by Labour.
"Patients are waiting weeks and weeks for vital heart scans. One in seven people in Wales is on an NHS waiting list.
"A Cancer Drugs Fund in England - but not here.
"I tell you - when Offa's Dyke becomes the line between life and death, we are witnessing a national scandal.
"After this utter shambles Labour should never dare call themselves the party of the NHS again."
Health is one of 20 areas devolved to the Welsh Assembly.
The different policies pursued by Labour in Wales include universal free prescriptions and looking to drive up organ donation rates by changing to an opt-out rather than opt-in system.
However, First Minister Mr Jones' government has come under fire amid claims it has under-funded the NHS.
And new statistics published this week showed that more Welsh hospital patients were waiting longer for diagnostic tests than in England, Scotland and Northern Ireland.
Mr Cameron believes Welsh Labour should take a leaf out of the Tories' book on health as well as education.
"We're arguing for more funding, more transparency, more power to doctors and nurses," he said.
"In education we're saying: in a competitive world it's not softer subjects and experimental teaching these children need...it's proper spelling in English, basic arithmetic in maths, the best of our history, proper respected exams.
"It's not more of this failed, left-wing, ideological clap-trap we need - it's more rigour, more standards, more choice, more hope."
The PM also insisted his Westminster government was making a real difference to people's lives.
He said the Tories had ensured the electrification of the Great Western railway-line went ahead as well as ensuring Japanese firm Hitachi signed on the dotted line for the Wylfa nuclear power station upgrade.
He added: "And the M4, the artery for thousands of Welsh businesses - it's finally going to get the work it needs. "
The Prime Minister also reaffirmed his commitment to income tax powers being devolved to Wales.
He added: "I believe in the Welsh Government being more responsible for raising the money it spends.
"And above all, I believe in the Conservatives campaigning as the one and only low-tax party in Wales today.
"We know it's not Government's money - it's your money - and we want you to keep more of it."
He also said the upcoming Nato summit in Newport this September was a chance for Wales to shine on the worldwide stage.
"London had the Olympics, Northern Ireland hosted the G8, the Commonwealth Games are in Scotland; now it's Wales' turn," he said.
"This is a vital summit. The biggest-ever in Britain's history.
"And with the situation in Ukraine, the world will be watching and asking.
"Do we still stand up to aggression, do we pledge our collective efforts to defend our allies..
"Do we believe in the future of Nato that's kept the peace in Europe for 65 years?
"I say a huge "yes" - and we'll be saying that here in Wales."
Mr Cameron also spelled out his party's long term five-point plan - which consisted of reducing the deficit, cutting income tax, creating more jobs, capping welfare and immigration and driving up education standards.
He added: "Our economy is one of the fastest growing in the developed world.
"The deficit is down by a third. Mortgage rates are at historic lows.
"Income taxes have been cut for 1.2 million people in Wales...and from this week, 144,000 of them will pay no income tax at all."
He also said unemployment in Wales had reduced by 32,000 people since his party came to power in Westminster and justified his party's unpopular austerity policies - saying they were necessary because no-one would "invest in a country crippled by debt".
Mr Cameron also paid particular tribute to the staff at Westbridge Furniture in Holywell, Flintshire.
Earlier in the day he visited the company's factory - where around 2,000 suites are made per week for customers such as Ikea and John Lewis - and met some of the firm's 400 staff.
"They are so proud of their craft and the job they do," he said. "These are the people of Wales. Enterprising, inventive, ambitious."
Earlier in the day, UK Health Secretary Jeremy Hunt launched his strongest attack on the NHS in Wales claiming it was "sleepwalking to a Mid Staffs tragedy".
He said: "If you ignore the evidence when individual problems pile up, if you stick your head in the sand and pretend all will be fine... well, that's exactly what happened at Mid Staffs under the last Labour government in England.
"And that is what the Labour government in Cardiff is risking right now in Wales.
"They are sleepwalking into a Welsh Mid Staffs tragedy and unless we shout loud enough these appalling lapses in care will repeat themselves time after time."
His comments came on the day the key and independent Nuffield report said NHS funding cuts may be behind longer waiting times, but added Wales was not lagging behind the rest of the UK.
Labour MP and shadow Welsh secretary, Owen Smith, said Mr Cameron's attack on the Welsh NHS was "baseless".
" It is ridiculous of the Prime Minister to describe Offa's Dyke as a 'border between life and death' - remarks beyond parody and beneath contempt - and especially so on the very day that an independent, Nuffield Trust study confirmed that there is little difference in health outcomes between the Health Services of England and Wales.
"Recent Tory scaremongering about the level of care received by patients in the Welsh NHS has been truly disgraceful, however, David Cameron has reached a new low with these comments.
"He should apologise to the thousands of Welsh health workers whose service he denigrates with his glib and baseless attacks, and even more so to the millions of people who use the Welsh NHS.
"The national scandal here is not the Welsh NHS, but David Cameron himself, who demeans his office with these remarks and who has clearly forgone any ambition to be a Prime Minister for the whole of Britain."