The former Toffees goalkeeper has criticised Bill Kenwright and co.
Manager Martinez is reportedly on the brink of being sacked, with Everton all but consigned to a bottom half finish in the Premier League and trophyless once more.
But the legendary former Toffees goalkeeper has blamed the club's board, in particular chairman Bill Kenwright, for failing to provide the Spaniard with a proper support network such as the one Sir Philip Carter had in place for Howard Kendall.
"I look at Roberto and go: OK Roberto, you’ve been brought in. Where’s your back-up, where’s your support, where’s your people behind you?" Southall told Radio City Talk.
"It’s almost to me like they’ve given him a boat to sail, and took the rudder off... and tried to get him to another island without the rudder. He’s making do and mending all over the place.
"I look at Howard and I look at Sir Philip Carter and I look at their relationship. Then I look at these two (Kenwright and Martinez) and I think Roberto’s been let down by the people at the top.
"At the moment there’s so much uncertainty about Roberto, it’s really unfair to him. And I know everyone says we should have had a better season… well yeah of course we should, I think he’s the first to realise it."
Despite being 11th, only six teams have actually outscored Everton in this season's Premier League and the Toffees' perceived underachievement is widely attributed to a defence which is the seventh leakiest in the entire division.
The 57-year-old added: "I’m thinking in terms of around Christmas, when we went on a bad run, somebody should have pulled him - and I’m sure Sir Philip Carter would have had a word with Howard - and said look Roberto, there’s only one bit of this team letting you down, get somebody in to coach your defence.
"That does two things for Roberto. He goes: OK now the pressure’s on this fella, he’ll change that defence for me. If it doesn’t work it’s that fella’s fault - pressure off Roberto. If it does work… well done Roberto, you’ve brought somebody in.
"Politically, I think he’s been let down."
Southall played 750 times for Everton throughout 17 years of service, during which time he was a First Division and FA Cup winner on two occasions and also lifted the European Cup Winners' Cup.
The Toffees' FA Cup defeat to Manchester United on Saturday ended their hopes of a first piece of silverware since the Welshman's team tasted success in the same competition 21 years ago.