The medical director of the NHS in England has called for mortality rates and waiting times in Welsh hospitals to be investigated.
Sir Bruce Keogh wrote to Chris Jones, who runs the Welsh NHS, with his concerns.
His e-mail mentions six Welsh hospitals that he describes as having a 'persistently high mortality rate.'
The Welsh Government says the NHS in Wales is "open, transparent and has a higher level of scrutiny than any other part of the UK", adding that comparisons on A&E waiting times and mortality rates cannot be made between England and Wales as both sets of data are calculated differently.
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