The UK Department for Work and Pensions (DWP) has denied that it is sitting on up to £1.5 billion worth of unused IPv4 addresses, claiming that the majority are being used internally.

Earlier this week, the RIPE NCC, which allocates IP addresses in Europe, the Middle East and parts of Central Asia, opened up its last block of IPv4 addresses, signalling a new milestone in the Internet’s transition to a new address scheme, IPv6.

“It's the end of an era, and also the beginning of the next stage in Internet history,” said Axel Pawlik, managing director at RIPE NCC.

However, coder and blogger John Graham-Cunning discovered that the DWP had control of an /8 block of IPv4 addresses – equating to roughly 16.8 million individual addresses – that he suggested was “completely unused”.

The /8 block could be worth between $500 million and $1.5 billion, he argued in a blog post, based on a US company's recent attempt to sell a /8 through a broker called Addrex.

According to a DWP spokesman, however, the vast majority of these IP addresses have been allocated within the department, adding that “there is no legitimate way for organisations with public IP address allocations to sell or trade those allocations on the open market”.

He pointed to a December 2011 response to a Freedom of Information request, in which the DWP said that approximately 80% of the address space had been allocated, and that the remaining space had been earmarked for use within the Public Services Network (PSN).

“DWP are aware that the worldwide IPv4 address space is almost exhausted, but knows that in the short to medium term there are mechanisms available to ISPs that will allow continued expansion of the Internet, and believes that in the long term a transition to IPv6 will resolve address exhaustion,” it said.

“Note that even if DWP were able to release their address space, this would only delay IPv4 address exhaustion by a number of months.”

In spite of the protests, however, an e-petition has been launched demanding that the DWP sell its block IPv4 addresses to help alleviate the shortage and reduce the government deficit.

The petition suggests that if the addresses are being used for internal private networks then this is a “phenomenal waste of public funds,” as a separate /8 block has been specifically earmarked for this purpose, and “using the globally routed internally is madness”.

The petition had 1,109 signatures at the time of writing.

Cambridge MP Julian Huppert has announced via Twitter that he will be tabling a question about the DWP's use of this block of addresses.