Health expert Marcus Longley warned that changes to the NHS in Wales, with fewer major A&E departments, could make the pressure on ambulances transferring patients worse, as response distances and times are increased.
Professor Longley said, though, that current problems lie within the system more broadly, and "the health service needs to get ahead of the problem, rather than just forever scrambling to catch up with it."
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The peer will attack Prime Minister Theresa May for failing to represent the 48% who voted in favour of Remain.
Paul Flynn, MP for Newport West, will open the debate in Westminster Hall.
It will represent another boost to the region, after the announcement Deca Sealand was chosen for a repair hub for defence aircraft.