Justin Bieber Accused of Faking Illness to Skip His Deposition

Justin Bieber got busted calling in sick for a deposition ... or so claim the lawyers who say they have proof he stood them up due to a night of heavy partying.

The attorneys are repping a songwriter who claims Bieber jacked a sample for "Sorry" -- and had scheduled a Feb 8 depo with Justin. According to docs, obtained by TMZ, Justin's team informed the lawyers just hours beforehand ... he wouldn't be able to because he was "ill."

Mind you, the lawyers say they'd flown to L.A. from Nashville to make it easier for Justin.

They got pissed when they found YouTube videos of JB chugging beers at Bootsy Bellows in the early morning hours of the very day he was supposed to be at the depo. The videos, apparently posted by Beliebers, show Justin drinking at a house party as well as the nightclub.

In docs, they say Justin rubbed their noses in it by posting Instagram pics drinking with friends ... hours after he played hooky.

They're willing to let him make it up, but now they want the court to force Justin to fly to Nashville in early March, and do the depo on their turf.

We reached out to Justin's team ... no word back.