(that's a) likely story
A phrase used to express disbelief of an excuse or explanation. He said he had to stay late at the office again. That's a likely story—he's probably out with his friends! The cat ate your science project? Likely story.
likely story
An exclamation of distrust or disbelief in someone's explanation or story. Albert: "Sorry I'm late. My car broke down half way here!" Sarah: "Yeah, likely story! I bet you just wanted to finish watching the football game on TV."