Welsh Ambulance pressures 'gone through roof' - Unite
The Welsh Ambulance Service is buying 41 new vehicles as it upgrades its 736-strong fleet for just under £4m.
The ambulance service has regularly failed to meet its target that 65% of ambulances should reach life-threatening incidents in eight minutes.
Just 53% hit the target in June, down from 54.1% in May, while July's figures are due to be published later.
The Welsh Conservatives say the upgrade was "unlikely to deliver the sort of step change in performance" needed.
Steve Sloan, regional officer for Unite with responsibility for the Welsh Ambulance Service, told BBC Radio Wales that demands on the service had "gone through the roof".
Pressures were due to an ageing and an unhealthy population, but he said there needed to be investment in more "two legged resources" with new recruits only replacing older crew who were retiring.