The Toffees have severely under-performed this season and they were beaten 2-1 by Swansea City in their most recent fixture.
At the moment Everton are in 12th place in the Premier League table and Merson has criticised Martinez for failing to address his side’s defensive issues.
“If you want to come middle of the table, keep playing they way they are playing. It’s entertaining, and it’s great for the neutral,” Merson said.
“If you want to be successful - you won’t be, playing like that. You have to keep clean sheets.
“They’re a good team, but he had that situation at Wigan. They got relegated. Everton aren’t getting relegated, but Wigan’s defence never improved and he hasn’t improved it here.
“You’ve got one of the best centre backs in world football, and they still let in all these goals. They have one of the best left backs around, they play with two holding midfielders, they have a good defender in Jagielka. “You have to go to the manager, and say ‘what are you seeing and what’s your philosophy?’”
Only five teams in the Premier League have conceded more goals than Everton this season.
The Toffees have also been guilty of throwing away leads when in strong positions, and they look set to perform well below their expectations.
Martinez’s side may have only lost six matches, but they have only won on six occasions too, and their tendency to allow opposition sides back into matches has come back to haunt them time and again.
Everton’s supporters have become frustrated with Martinez’s approach, and the pressure is now on the Spaniard to start resolving an issue which has been evident for far too long before it is too late.