Hi kuwait340.
I'm a controller in the US. I don't know what requirements controllers in your part of the world must abide by, but here our requirements for speed reduction and altitude change are pretty explicit: don't issue a simultaneous descent clearance and speed adjustment.
Here is a snippet from the manual US controllers use, the 7110.65: found at this link:
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c. Simultaneous speed reduction and descent can be extremely difficult, particularly for turbojet aircraft. Specifying which action is to be accomplished first removes any doubt the pilot may have as to controller intent or priority. Specify which action is expected first when combining speed reduction with a descent clearance.
1. Speed reductions prior to descent.
PHRASEOLOGY-
REDUCE SPEED:
TO (specified speed),
or
(number of knots) KNOTS.
THEN, DESCEND AND MAINTAIN (altitude).
2. Speed reduction following descent.
PHRASEOLOGY-
DESCEND AND MAINTAIN (altitude).
THEN, REDUCE SPEED:
TO (specified speed in knots),
or
TO MACH (Mach number),
or
(number of knots) KNOTS.
NOTE-
When specifying descent prior to speed reduction, consider the maximum speed requirements specified in 14 CFR Section 91.117. It may be necessary for the pilot to level off temporarily and reduce speed prior to descending below 10,000 feet MSL.
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Here's a link to the whole section on speed control phraseology and procedures adhered to by US ATC:
http://www.faa.gov/airports_airtraff...5/atc0507.html My ATC brother at your home base may have similar requirements. Hope this helps. If I'm butting in where I don't belong, please excuse me.
Happy flying!