The leaked files include documents, detailed data and private e-mails exchanged between leading climate scientists.
But academics deny claims the material showed science had been manipulated.
Professor Phil Jones, who has stood down as director of the Climatic Research Unit (CRU) while the review takes place, has said he stands by his data and insisted that the emails had been taken "completely out of context".
In a statement, Deputy Information Commissioner Graham Smith said it was an offence under section 77 of the Freedom of Information act "to prevent intentionally the disclosure of requested information".
He said the requests were made by a climate change sceptic in the 2007-2008 period and as the case was more than six months old "the opportunity to consider a prosecution was long gone" under existing legislation.
Mr Smith said the ICO was "gathering evidence from this and other time-barred cases to support the case for a change in the law".
He added: "We will be advising the university about the importance of effective records management and their legal obligations in respect of future requests for information."
In a statement, Professor Edward Acton, vice-chancellor of UEA commented: "We have not received any further information from the ICO although we are urgently trying to contact them.
"The ICO's opinion that we had breached the terms of Section 77 is a source of grave concern to the university as we would always seek to comply with the terms of the Act.
"During this case we have sought the advice of the ICO and responded fully to any requests for information."
Norfolk Police have launched an inquiry into the emails case.
Meanwhile, former civil servant Sir Muir Russell is heading an independent review to examine whether there is evidence that data was manipulated or suppressed in a way which was "at odds with acceptable scientific practice".
The former chancellor Lord Lawson has called for the CRU inquiry to be conducted in public wherever possible.
Lord Lawson, who is chairman of the Global Warming Policy Foundation think tank, also said the terms of reference needed to be broadened to cover the external impact of the e-mails.
In a letter to Sir Muir, he referred to e-mails that are alleged to show scientists from UEA conspiring against other researchers.
"As well as taking evidence from those in CRU who wish to clear their names, you should go outside CRU and take evidence from those who feel they or their work have been improperly treated," Lord Lawson wrote.
He added: "The damage to the public interest can be just as much from what was suppressed as from what was incorrectly published."
The UEA said the inquiry would also explore how freedom of information requests had been acted on.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.