Police said the Stanwell Tops couple were in a maroon Ford Laser travelling south along the Princes Highway at 1am.

Police allege they were struck from behind by a silver Mazda 2, driven by a 22-year-old woman from Maroubra.

The Laser then left the road and hit a tree, trapping both the male driver and the female passenger.

The man was airlifted to St George Hospital in a critical condition.

The female passenger, also critical, was taken by ambulance to St George Hospital.

They were still in a critical condition on Sunday afternoon.

The 22-year-old Mazda 2 driver was uninjured and, after returning a positive roadside breath test, was taken to Sutherland Police Station.

After a breath analysis, Police allege the woman returned a reading of 0.090.

She was later charged with mid-range PCA and will appear in Sutherland Local Court on June 23.