The Irish Council for Civil Liberties (ICCL) has said a new safety bill could severely impact people's ability to express themselves online in an unintended way.
The Online Safety and Media Regulation Bill is implementing an EU directive, and proposes to restrict non-illegal speech online.
However the ICCL has said there are dangers in restricting speech that may be distasteful, but does not break any laws.
Executive director of ICCL, Liam Herrick, told Newstalk Breakfast the scope of the bill is too large.
"Everybody recognises that there needs to be more State regulation and oversight of what happens online, and social media in particular.
"And there's aspects of this proposed legislation which are clearly going in the right direction - particularly around criminal content, for example child sexual abuse material.
"The challenge I think is that you need to strike a balance between attacking and regulating criminal content, but also protecting freedom of expression".
He said the ICCL believes the way the bill is drawn up could "in an unintended way have severe impacts on our ability to express ourselves online and also in terms of private messaging".
He said any new sanctions have to be clear and precise.
"Whereas the bill proposes to define harmful content as including material that's a criminal offence... also will regulate material that is likely to have the effect of intimidating, threatening, humiliating or persecuting a person to which it pertains.
"That is potentially very broad, very vague - it's introducing concepts that aren't particularly known to law.
"The danger here is that this could be interpreted so broadly that it will have a chilling effect on people being able to express themselves and engage in critical discourse online".
Role of new regulator 'wholly unclear'
He said this could see take-down notices issued, or people could be restricted from making certain expressions.
The bill also proposes to create a new regulator, whose role the ICCL has said "is wholly unclear".
Mr Herrick said this is too much power for one such body.
"It's proposing, essentially, a super-regulator - a new Media Commission that would replace the Broadcasting Authority of Ireland, and also take on huge new functions in relation to the online realm.
"It's proposing that this new body would be able to both set codes and define what is harmful content, and then also enforce it.
"We think this really is an over-reach: this new body will have far too many powers, and will be both setting the law and enforcing the law".
The ICCL said other possible approaches should be considered - including establishing a system that would allow social media platforms and other online service providers to opt-in to an online harms code, with specific attention given to children.