"Jonny Bairstow will be fine batting at number seven but I would worry immensely if he has to keep in a Test match," Vaughan told Sky Sports News. "I wouldn't put him in the top five keepers in England.
"I questioned it as soon as the squad was selected. I just don't think he's done enough of it to withstand the pressure of an Ashes series keeping wicket. Bairstow is a package that could work in 20-over and 50-over cricket, but in five-day cricket, yes you need someone who can bat, but also to take those important catches.
"He hasn't done enough for Yorkshire this summer because he has been playing for England. He may have to keep in the hottest of pressure zones, the Gabba, in front of 40,000 spectators. The selectors feel Bairstow is the next best, but I would question that."
The Ashes gets underway in Brisbane next week.