Asad Shafiq (22 not out) and Babar Azam (23 not out) ensured the Pakistan run rate picked up again, steering their side to 5-155 at lunch with a lead of 435.
They were only able to add 110 runs before lunch but have a complete stranglehold on the game, leaving Australia fighting for survival when they try to save the match in their second innings.
Missing suspended duo Steve Smith and David Warner, Australia’s top six in Dubai included three debutants in Aaron Finch, Travis Head and Labuschagne.
Finch (62) built a strong opening partnership with Usman Khawaja (85) but Head and Labuschagne both made ducks with Shaun and Mitch Marsh – batting at No.3 and No.4 respectively – also dismissed cheaply.
The inclusion of three debutant batsmen was always going to be a gamble in difficult conditions but similar capitulations on subcontinental turning tracks in recent years suggest the performance in Dubai was far from isolated.
Finch conceded Australia’s batsmen had struggled to counter Bilal Asif’s (6-80) spin but denied panic had set in as the wickets began to fall.
“I think all the guys who walked in still had really clear plans with what they wanted to do and what they’ve been practising,” Finch said.
“It’s just a different environment when you walk out and there’s guys all around the bat, which is tough to replicate in the nets.
“A guy who is a very tall off-spinner (Bilal) getting a lot of bounce, which is hard to replicate.
“Guys still had really good plans, and your first 20 or 30 balls in these conditions are obviously your most vulnerable.
“It’s just about being patient, making sure that we’re still making good decisions and (taking the) opportunity to go on.”
Finch rued that neither he nor Khawaja were able to reach triple figures, saying it had been their responsibility not to allow Pakistan’s bowlers fresh targets at both ends.
The pair’s 142-run stand was Australia’s second-highest opening partnership in Asia.
“Myself and Ussie today not really going on and getting huge scores, that probably leaves us hanging a bit,” Finch said.
“That was probably the biggest mistake we made today.”
Head lasted just nine balls in his maiden Test innings and Labuschagne two as Australia’s hopes of getting close to Pakistan’s imposing first-innings total of 482 slipped away.
Australia have only won on three occasions in Test cricket after conceding at least 482 runs in the first innings.
AAP, with Phil Lutton