General Petrol leaking near tank

[cee em dee]

My 1998 Mk1 Punto 1.2 8v is leaking fuel underneath the car near the tank. The car has been 'Laid up' for just over 12 months. I had put a new battery in and had put the key to show the dash lights without actually starting. I could smell the petrol then and discovered the leak, which appears to be coming from a small plastic unit near where the pipe from the filler cap goes under the car. This seemed to stop when i turned the ignition off. Started the car ( which fired up first time, incidentally ) and the dripping seemed to increase. What is this unit ? and is it possibly a plastic pipe leak. Help !!

 

[850SPECIAL]

Hi Petrol will be coming from fuel filter. Some are metal some are plastic .Metal one rusts due to being close to o/s rear wheel and age .Done my sons last week it to is a 98.It has a metal type jubilee clip holding it in place will be rusted in so just cut it off and replace with new one 15min job less than £10.