Help Key/Imobiliser Trouble

Can anyone help, I have a Fiat Palio weekend, when I put the key in the ignition and turn it the key light stays on with the word code. When I try to start it up it turns over but wont start so I have to fiddle with the key in and out of the ignition a few times for the light to go out and then it starts, but this can happen all drive when I'm out and about and then it dos'nt happen again for a week or so, I can be messing with it for 5 to ten minutes trying to get the ignition light out. Any advice would be most appreciated, by the way I have not got the master red key only the two blue ones.

Ann