The introduction of age verification measures on porn sites to prevent underage internet users seeing explicit content is expected to be delayed for a second time, it has been reported.

The changes, the first of their kind anywhere in the world, were due to come into force on July 15, requiring porn sites by law to carry out “robust age-verification checks on users”.

According to the BBC, Culture Secretary Jeremy Wright is expected to tell the Commons on Thursday that the date will be pushed back, having already been delayed from April last year.

The reason for the delay is not clear, the corporation said.

However, Sky News said it understood the delay was “bureaucratic”.

It reported that the Department for Digital, Culture, Media and Sport had failed to notify the European Commission of key details.

Sky News also said it had seen a copy of a letter to regulator the British Board of Film Classification from a lobby group representing online pornographers, warning that without a delay there would be “less protection for public data”.

Under the plans, websites that fail to implement the rules face having payment services withdrawn or being blocked for UK internet users.

The government has previously said that users will be able to verify their age in a number of ways, including using traditional forms of ID such as a credit card or passport, or by buying an over-the-counter card from shops where verification would take place face-to-face.

Announcing the measures in April, Digital Minister Margot James said: “Adult content is currently far too easy for children to access online. The introduction of mandatory age-verification is a world-first and we’ve taken the time to balance privacy concerns with the need to protect children from inappropriate content.

“We want the UK to be the safest place in the world to be online and these new laws will help us achieve this.”

Campaigners have raised concerns over the tools, however, warning that they could have consequences for user privacy.

After the April announcement, Jim Killock, of the Open Rights Group, said on Twitter: “#ageverification dangers are obvious, from outing people to ruining careers and even suicides.

“What porn you watch can be very sensitive information. It’s striking that MPs don’t seem concerned, it’s not like public knowledge about watching porn has never impacted an MPs career.”

The Government said alongside requirements for age-verification providers to comply with the General Data Protection Regulation (GDPR), it had created a voluntary certification scheme, the Age-verification Certificate (AVC), which will assess the data security standards of the providers.