Prime minister David Cameron 'degrading' NHS in Wales
Staff morale is being damaged by criticisms of the NHS in Wales, a nursing chief has told the prime minister.
Royal College of Nursing head Dr Peter Carter told David Cameron in a letter staff were hugely frustrated.
Last year, Mr Cameron said differences in NHS performance in Wales and England meant Offa's Dyke was a "line between line and death".
Welsh Conservatives said it was their duty to hold ministers to account.
In his letter, Dr Carter wrote: "This is of huge frustration and disappointment to nursing staff who are working tirelessly to care for patients in often difficult circumstances.
"The RCN is concerned that the effect of these remarks is causing further demoralisation of the workforce, at a time when nursing morale is already at an all time low.
"Comparative evidence of the health systems of all four countries actually shows that the performance gap is the narrowest it has ever been, and with no universal indicator to accurately compare performance, constant degrading and criticism is unhelpful."
A spokesman for the Welsh Conservatives said: "We are the only party to consistently oppose Labour's record-breaking NHS cuts, which have seen beds axed, services centralised and hospitals downgraded, all heaping pressure on staff, leading one nurse to recently compare stress levels in the Welsh NHS to the frontline in Iraq.
"As a constructive opposition, it is our duty to hold Labour ministers and health bosses to account and we will continue to put forward proposals to protect and improve the NHS for staff and patients."