Originally Posted by
IO540
in which case ATC should not issue an SVFR clearance if the met vis is below 3000m .
Not so. A CPL (no IR) holder can, I believe, accept a SVFR clearance with a min vis of 1800m. Therefore ATC can not issue a SVFR clearance with a vis of less than 1800m, or a cloud base of less than 600'. ATC are not aware of what licence/ratings a pilot has and are not permitted to ask.
Also VMC minima vary according to the class of airspace, e.g. in the UK min vis of 5km in class D, 1500m in class G.