A House of Lords committee has called for greater detail on how the UK government intends to introduce online porn age verification plans in the Digital Economy Bill.
Under the proposed legislation, pornographic websites that fail to implement checks would be blocked by all UK internet service providers.
The Digital Econonomy Bill has been passed by MPs and is now due to enter the committee stage, which will examine the legislation.
But the committee said the Bill does not spell out "how the age-verification regime will actually work."
Guidelines for age checks are to be drafted by an "as yet-to-be-designated regulator" which could adversely affect the ability of the House "effectively to scrutinise the legislation", it said.
"Our concern is exacerbated by the fact that, as the Bill currently stands, the guidance and guidelines will come into effect without any parliamentary scrutiny at all.
"The House may wish to consider whether it would be appropriate for a greater degree of detail to be included on the face of the bill."
Fears have been raised that age checks could require significant policy changes.
Information Commissioner Elizabeth Denham said in her evidence to the Public Bill Committee she would “have significant concerns about any method of age verification that requires the collection and retention of documents such as a copy of passports, driving licences... which are vulnerable to misuse and/or attractive to disreputable third parties.”
Last week the UN’s free speech advocate said censorship of pornographic websites risks breaking international human rights law and would contribute to a “significant tightening of control over the internet”.
The Liberal Democrats have also oppose the plans describing the measures as something the "Russian or Chinese governments" would impose.
The Bill has also been criticised for its proposals to increase the government's sharing of personal data. Academics and privacy campaigners signed an open letter calling for those measures to be removed. ®