The chairman of the ISC, Sir Malcolm Rifkind, announced the expansion in a public statement, arguing that businesses' and citizens' ongoing concerns over the data-monitoring powers held by Government Commnications Headquarters (GCHQ) will only be allayed if all parties are included in the investigation.
"In recent months concern has been expressed at the suggested extent of the capabilities available to the intelligence agencies and the impact upon people's privacy as the agencies seek to find the needles in the haystacks that might be crucial to safeguarding national security. There is a balance to be found between our individual right to privacy and our collective right to security. An informed and responsible debate is needed," he said.
Rifkind said the UK parliament and ISC would now begin expanding scope of the inquiry and begin accepting feedback from the public. "The Intelligence and Security Committee of parliament has therefore decided to broaden the scope of its forthcoming inquiry to consider these wider questions, in addition to those relating to the existing legislative framework," he explained.
"In addition to the classified information that only the ISC has access to, the Committee will also be inviting written evidence more broadly, including from the public, to ensure that the Committee can consider the full range of opinions expressed on these topics. Once it has considered those written submissions it will also hold oral evidence sessions, some of which it expects to hold in public."
The ISC initially cleared the GCHQ of any wrongdoing regarding PRISM in July. The initial investigation only focused on the question of whether the types of data collected and how it was collected by the GCHQ broke existing UK laws.
News of the PRISM scandal broke earlier in the year when ex-CIA analyst Edward Snowden leaked classified documents to the press proving that the US National Security Agency (NSA) was gathering vast amounts of web user data from companies such as Google, Facebook, Yahoo and Microsoft. The scandal led to a global debate on existing privacy laws. The European Court of Human Rights is also investigating GCHQ's involvement in the PRISM spying scandal.
The expanded investigation follows widespread calls for a public debate about intelligence agencies' data collection powers. Ex-Navy Seal and Silent Circle chief executive Mike Janke called for a public debate about what powers the NSA and GCHQ should have in interview with V3 in August. Renowned cryptographer Bruce Schneier made a similar call to arms, accusing the NSA of "commandeering the internet" in a public blog post.