Fergie issued a public apology about his comments but Leighton has not been imprressed by that and thinks that Fergie should face a UEFA-style coaching ban as punishment.
"I think it's a half-hearted apology at best really, and it probably exacerbates the position, rather than resolving it," Leighton told BBC Radio Five Live.
"He clearly hasn't retracted the statement about Alan being unfit so it's not an apology for the main offence caused - and then he widens it to question the fitness of other referees, so he seems to be opening another can of worms which I don't think is very helpful at all.
"Referees are very fit...they have sports scientists who test them regularly throughout the season. They don't just pass a fitness test at the start of the season.
"Their body fats and BMI are regularly monitored, there are get-togethers every two or three weeks where they are put through extensive training and testing."
"I think the punishment should be a UEFA-type coaching ban, which is rather more than a touchline ban.
"Referees always accept decisions are going to be pored over - they have no problem with legitimate criticism.
"What's problematic is when the integrity and key components of refereeing are being questioned in a totally unwarranted and unfounded way - and we will defend our members when they are."