Communications Minister Michelle Rowland introduced the world-leading reform to parliament last Thursday, which she said would make the online environment better for young people.
The consultation period for groups and individuals to make submissions closed a day later on Friday.
A senate committee on Monday held a one-day hearing and is due to report back on Tuesday.
X says one day is not a reasonable period of time to make a submission to proposed law changes. (Joel Carrett/AAP PHOTOS)
The coalition has said it would reserve its final decision on the bill until answers had been received from the government.
In submissions to the inquiry, a number of groups, including social media companies, pointed to the short notice period.
Snap Inc, wrote the "the extremely compressed timeline" had allowed stakeholders little more than 24 hours to provide a response which "severely" constrained thorough analysis and informed debate.
"Due to this rushed process, we have not had time to set out substantive feedback on crucial elements of the bill," it said.
"We could of course address these in much more detail if this inquiry was afforded more time in keeping with established Parliamentary norms."
X, formerly Twitter, also criticised the "unreasonably short time-frame of one day".
"We have serious concerns as to the lawfulness of the bill, including its compatibility with other regulations and laws, including international human rights treaties to which Australia is a signatory, as further detailed below," it wrote.
Meta, which owns Facebook, wrote there had been "minimal consultation or engagement" and urged the government to wait for the results of the age assurance trial before progressing with the legislation.
TikTok said despite the "time-limited review" there were a range of "serious, unresolved problems" that the government must clarify to ensure there wouldn't be unintended consequences for all Australians.
The proposed laws will come into effect a year from when they pass parliament.
