Two objects?

Are there two objects here?

Blame the crisis on the banks.

You mean something like:

"banks" -- object of "on"
"crisis" -- object of "blame"

?

Crisis is the direct object and banks is an indirect object.

[Blame (the crisis)] {on the banks}.

You could also say "[Blame (the banks)] {for the crisis}," which would switch the objects around so that crisis would be an indirect object and banks would be the direct object.

[] = verb phrase
() = noun phrase
{} = prepositional phrase

Yes, there are two objects.

*
{} = prepositional phrase *

But isn't "blame for" a prepositional verb?

How is it a prepositional verb? You can easily replace the prepositional phrase with another phrase, like "due to their greed" or "while they let money slip through their fingers," or just leave off the prepositional phrase altogether: "Blame the banks."

The "for" is implicit in "Blame the banks", Entbark.