Gas hob problem?? Everytime I light the gas hob the flame starts stale green, the...

Everytime I light the gas hob the flame starts stale green, the pressure varies respectively time it is turned on also the flame keeps going out, disappearing gas leaking into the room as we don't other realise straight away!
Any advice would be particularly welcome thankyou.
Answers:    Sounds similar to you have a blockage surrounded by the injector, this can be dangerous, if it is your cooker, you will enjoy to sort it out, if it is the landlords cooker, ring him, if he doesn't respond within 24 hours, ring transco on 0800 111999, (if uk), they will probably turn sour the gas, you should have a copy of a landlords safekeeping certificate, except, ring corgi or go online to trustcorgi, they will chase him up. In the meantime, do not use any of the cooker rings that are a problem or even don't look right.
Make sure the cookier ignition is sparking to reading light the gas :)