SYDNEY, June 29 (Reuters) - Australia will introduce new legislation in parliament on Monday to strengthen restrictions on social media use for those under 16 and give the internet regulator broader powers to prosecute tech giants for non-compliance.

The move follows the imposition of the world's first restrictions of their kind, which came into effect in December, in a policy that many countries are watching closely in an effort to follow suit, with evidence that children are still able to access those platforms.

Prime Minister Anthony Albanese said that far too many children are still using social media, and that technology companies are not doing enough to comply with the law.

"This afternoon we will introduce legislation that goes further to ensure that social media companies do everything they can to prevent children under 16 from using their platforms," he told reporters in Canberra.

The regulatory body is investigating the potential non-compliance of five platforms: Facebook and Instagram (both owned by Meta), Snapchat, TikTok, and Google's YouTube.

Albanese called on the opposition conservative coalition to support the bill.

The amendments, announced on Sunday, will double the fines to A$99 million (US$68.2 million) from A$49.5 million.

Communications Minister Annika Wells said the amendments also give the eSafety Commissioner the power to demand documents such as minutes of corporate board meetings and internal emails, ensuring that cases brought against non-compliant platforms are "as strong as possible".

(US$1 = 1.4518 Australian dollars)