Cleared for approach prior to the IAF - when can you descend ?
Situation:
Aircraft has previously been cleared to a VOR at 5000', The VOR is the IAF for an approach where the outbound leg of the racetrack is a minimum altitude of 2600'. About 7 miles from the VOR, approach clearance is given.
When I learned in the US the FAR's were quite specific that in this situation you maintain your last assigned altitude until the IAF and then you can descend in accordance with the approach procedure and your clearance.
Where I'm flying now (Spain) it seems that eveybody is quite happy that once the approach clearance is received you can descend straight away to 2600' as long as that's not below MSA for the sector from which you're approaching the beacon. Is this in fact the correct thing to do ?
Can anybody point me to a reference to this in the AIP, PANS-OPS or something else official. I can't find one. I can find plenty of people who think they can reason why it should be OK to do this but not actually provide a reference.
Thanks in advance.