Although Wales caretaker coach Scott Johnson has released several other Llanelli players - including Mark Jones, Dafydd James and Matthew Watkins - for the Anglo-Welsh Cup encounter, Peel will not be risked just seven days before the Six Nations Championship appointment with Italy.
Under an agreement between the Welsh Rugby Union and Wales' four professional regional sides, a player expected to be on international starting duty can be stood down from club duties the previous week.
Peel's situation is accentuated by the fact Wales have already lost his long-term understudy Gareth Cooper for the rest of this season to a shoulder injury.
The Scarlets are desperate to have Peel on board against Bath - but they look like failing in their quest.
"That's a disappointment for me, because I rate him really highly," said Ashton.
"When you play sides like Llanelli you want all the big stars playing. You don't want guys who are world-class players sat on the touchline watching the game - that seems a bit silly in a semi-final.
"I think the way Nick Walshe has been playing for us - he's probably been the form number nine in the Guinness Premiership over the last four or five weeks - it would have been a great tussle between them."