The precise wording will be very important, which is why all of these pre-speech announcements tend to irritate me rather. Why not wait until he's actually said it? Ho hum.
In as much as Libyan intervention should have been more complete after the invasion, he is right. But, before Ed Miliband makes too much of this, he might care to wonder why it was that there was no enthusiasm for "boots on the ground" and a larger involvement. The main reason? at least as I see it, it's because the West lost its appetite for interventionalist foreign policy during and after the mess made in Iraq and Afghanistan. Several hundred deaths among UK forces and with little to show for it -- and several thousand deaths among US forces with the same lack of results -- have turned us off getting involved in foreign countries to any extent that puts soldiers' lives at risk. Even though it was necessary to have some forces in Libya after Gadaffi's fall to help ensure a stable aftermath, this was never an option people would have voted for, and so the leaders of NATO countries in particular felt they had to stay out.
If Miliband wants to assign any personal blame, then, he might care to look in Tony Blair's direction.