Fog Lights Turning Themselves On

[xtab]

I've just started having a very weird problem with my 2013 Focus Zetec.  When the vehcile is parked up, after a while the fog lights turn themselves on.  The time between this happening varies a lot.

I've tried leaving it unlocked, as well as locking with the key in case it's linked to that, but nothing makes any difference.

A google search hasn't brought up any similar stories.

Anyone any idea what might be the problem?

(The first night it was the dipped headlights, but for the past 24 hours it's been the fogs)