The pair have both started to receive regular opportunities at international level, but they have not always been given roles they are entirely familiar with.
Vardy has played out on the left wing, while Barkley has had to drop back into central midfield on occasions, and Collymore doesn’t feel that Roy Hodgson is getting the best out of either of them by doing that.
"Two or three good games in an over exposed Premier League and you’re the second coming, the answer to England’s poor technique, poor tournament play, poor anything and everything, but it does raise a genuine question," Collymore wrote on Boylesports' website. "When and how do you know when a player is ready for international football?
"For me there’s only one way, whether it’s a much touted prodigy like a Barkley, or a slow burner from non league like Vardy, we must give them at least six games, in the position they want to play in and let them sink or swim; something England have never done well. It’s time to change."
Vardy’s form for Leicester has forced him into the England team, with the 28-year-old striker now boasting the best scoring record in the Premier League.
Vardy already tops the top-flight scoring charts, but he has picked up a knock recently and had to miss out on England’s qualifying against Spain on Friday night.
Barkley, meanwhile, has been tipped to have a big future at both club and international level, and he has shown his class this season.
The attacking midfielder has been in superb form for Everton, while he has also shown his quality for England – scoring against Lithuania in his nation’s last competitive match.