Frolli 77FF combination boiler wont ignitenation boiler won't ignite?

The pilot light will not stay alight. When the igniter is pushed the pilot light comes on but as soon as it is released it goes off. When the boiler is in the continuous hot water and central heating mode, the pilot light sometimes stays on and both the hot water and central heating works for a short while and then stops with the pilot light also going off.