Holt has scored 13 goals during his debut season in the Premier League, making him the second-highest English goalscorer behind Manchester United's Wayne Rooney.
Welsh international Morison has joined the growing number of calls for Holt to be handed a spot on the plane for the tournament later this summer.
"If he doesn't get called up to the Euros, it will be a travesty," Morison told talkSPORT.
"I hear people talking about other players in the league and you have only got to look at the top goalscorers chart. That is what you go by. You go by players who are playing well, players who are scoring goals, and he is doing everything.
"With some of the players who have been called up in the past and given a chance, if he doesn't at least get a chance it will be an absolute disgrace."
Holt, 30, joined the Canaries in 2009 from Shrewsbury Town.