It was not clear what Ecclestone, 77, was specifically referring to; McLaren's involvement in the espionage scandal, the spat with former teammate Alonso, strategy errors such as the decision to leave Hamilton on worn tyres in China, or the technical fault in Brazil.
"Lewis could have won the championship last season, but the team let him down," Ecclestone said in an interview with the Spanish sports daily Marca.
Ecclestone also said he was happy to see Alonso back at Renault after a tumultuous single season with McLaren in 2007.
"I think he is going to be more at home there, because the truth is that he was not happy at all where he was," the Briton said.