An age-check scheme designed to stop under-18s viewing pornographic websites is expected to be delayed for a second time.
The changes - which mean UK internet users may have to prove their age - were due to start on 15 July after from April 2018.
While the government has not officially confirmed the postponement, it is expected to announce on Thursday that the date will be pushed back again.
The reason for the delay is not clear.
Culture Secretary Jeremy Wright is expected to make the announcement in the House of Commons later.
The plans for compulsory age-checks for UK porn viewers - which the government has described as a world-first - were aimed at protecting children from inappropriate content.
Pornographic sites will have to verify the age of UK visitors by law. If they fail to comply they will face being blocked by internet service providers.
There has been confusion over how it will be enforced, with suggestions that websites could ask users to upload scans of their passports or driving licences, or use age-verification cards sold by newsagents nicknamed "porn passes".
Campaigners have also repeatedly raised concerns about the privacy and security of the scheme.
Critics also say teens may find it relatively easy to bypass the restriction or could simply turn to porn-hosting platforms not covered by the law.
Twitter, Reddit and image-sharing community Imgur, for example, will not be required to administer the scheme because they fall under an exception where more than a third of a site or app's content must be pornographic to qualify.
Likewise, any platform that hosts pornography but does not do so on a commercial basis - meaning it does not charge a fee or make money from adverts or other activity - will not be affected.
Furthermore, it will remain legal to use virtual private networks (VPNs), which can make it seem like a UK-based computer is located elsewhere, to evade the age checks.
The authorities have, however, acknowledged that age-verification is "not a silver bullet" solution, but rather a means to make it less likely that children stumble across unsuitable material online.