On the face of it Jason (Muniz) and Marty (Giamatti) are not that different - both will bend the truth to get their way and lie outright if it will save their skins.

However, Jason is a 14-year-old schoolboy who considers he's just thinking on his feet while Marty Wolf is a hotshot Hollywood producer for whom the word truth is for wimps when there's a buck to be made.

Their paths collide when Jason's bicycle slams into Marty's stretch limo and his overdue English story Big Fat Liar is literally pitched into the Tinseltown high-flier's lap.

Jason - who is despatched to summer school by his despairing parents - thinks nothing of it until he sees the trailers for the forthcoming blockbuster Big Fat Liar which bears an alarming similarity to his school essay.

Hooking up with his best pal Kaylee (Bynes), he heads off to the Holllywood Hills to confront Marty with an ultimatum - either phone his dad and tell him what really happened to the story... or he'll spill the beans.

Of course, Marty meekly complies, picks up the phone, admits his blatant plagiarism to Jason's dad and sends the little fellah on his way.

Except he doesn't. The duplicitous movie executive welcomes the youngster into his lair, torches the evidence with his fat cat cigar and then turfs the disbelieving teenager onto the street.

However, Marty underestimates how much Jason is committed to winning back his parents' trust and to the lengths he'll go to get even with the studio schemer.

Muniz possesses that precious commodity - the ability to play an American teenager without creating a character that almost demands a cuff round the ear.

He manages to steer a course just on the right side of likeable brattishness, eschewing the usual high-fiving nonsense that condemns similar roles into an amorphous mass.

Giamatti has deftly handled a number of supporting roles (Saving Private Ryan, The Truman Show) but here he shows he's got what it takes to handle a leading part.

Marty Wolf is a wonderful creation - a power-crazed tyrant without the hint of a redemptive streak and Giamatti has every duplicitous move and double-dealing parry down pat.

Tim Evans