Whine when you press forward on the gear stick

I have a 2004 1.2 Renault Clio Dynamique. When you are driving along in any gear all is well. The problem I have is a whining noise (just like the gearbox is on the way out) but only when you push forward on the gear stick when in 5th gear. Also at any speed, press the clutch down, select 5th and push forward on the gear stick and the noise gets louder the harder you press. Let the clutch up and continue on your way all is fine. Any ideas team? Much appreciated.