I've answered this question elsewhere on this site. It's a faulty spark generator. They are easy to replace but you have to disconnect the gas pipe from the bayonet fitting at the rear of the cooker. As any gas work needs to be done by a registered Gas Safe installer you should leave it to a professional. Indesit (who now own Canon) will come out and do it but it will cost £100 plus.
JayGee, September 2010