there are many, but this one at 398 kb should probably work.
It's not "official", though. For official, you'll have to make your own geojson from here.
Earlier this year the "Land Cover Map of Europe 2017" with 10m pixel size has been published, see http://www.esa.int/Applications/Observing_the_Earth/Copernicus/Sentinel-2/Land-cover_maps_of_Europe_from_the_Cloud .
It is a pan-European map, yet potentially interesting for you due to its high spatial resolution.
At country level, you find for ...