Usually when they don't get changed for a while they get corroded
Doesn't really matter WHAT it is, the only course of action is to get it to a garage before someone walks past with a cigarette and kills you all.....
Either the filler pipe of fuel return pipe, much more expensive if you DON'T get it fixed
If the car has fuel injection the return pipe to the tank is damaged. You need a piece of fuel hose and 2 pipe clips. Easy fix. DIY with a screwdriver. Or £50 at a garage.
It could be a hose or a loose fitting. Or it could be something expensive that is damaged.
When I say leaking it pissed out £20 in 2 hours, it seems to be coming from the mid section of the underside of the car and only when the engine is running.
Any one got an approximate price to fix such a leak