HI folks, my girlfriends mark 3 fiesta N reg has started having problems when the clutch is down

eg when the cluthch is down it revs the nuts of the engine! There is no specific amounts of revs as it changes all the time

Also when driving at low speed you can feel the revs are still high as the car is pulling more than it should be for what they are when you drive at low speed.

Any suggestions??

Luke