RNAV Doubt
 

Let's say a pilot is following an RNAV SID and then realises that the NAV Accuracy has degraded below the required. The ATC is informed Unable RNAV. If then ATC then gives a Direct To to a Waypoint can the pilot accept it?

Pretty poor day when you were but are now not able to maintain 1 mile nav accuracy.

If I was given direct to a way point that I could verify via raw data, I was above the MSA for the area and I could quickly tune the required beacon for the required way point (or I already had it hard tuned) then I would be happy to accept. However if I was in any doubt whatsoever I'd insist on at least a heading but preferably a heading and a climb above MSA.