Ford Fiesta car unstable when turning left

My fiesta has recently started handling very badly when driving over uneven raod surfaces or turning left. The car starts to turn in but then the steering wheel pulls sharply and the car turns much tighter without any input from myself. I have had the car when up on jacks and checked the steering and suspension and everything seems tight and in place. The car does not have a front anti-roll bar and the rear suspension support all seems intact but I haven't been able to go so far as to check the shocks or associated bushes. When testing the steering with the front wheels off the ground there appears to be no play in the syetem? Any ideas?