The parliamentary ombudsman has backed the government's decision not to release legal advice on the Iraq war.

Number 10 has consistently refused to release the full details of the the attorney general's advice to the prime minister.

And in a series of adjudications released on Wednesday, Ann Abraham said the government was justified in refusing to release the information to the public.

She did, however, disclose that Lord Goldsmith's advice did not include any "presentational or policy advice".

Setting out its reasons for refusing to release the advice, the Cabinet Office said it was protected by legal professional privilege.

The department also said that it "was information whose disclosure would harm the frankness and candour of internal discussion, in particular because it was internal opinion and advice amounting to a highly confidential communication between the attorney general and the prime minister".

And the managing director of the Cabinet Office said that consideration had been given "as to whether or not in this case the harm to the frankness and candour of internal discussion was outweighed by the public interest in making the information available, but they had concluded that it was not".

Abraham's report said that there had been "some unfortunate initial confusion within the Cabinet Office, in particular the prime minister's office" about whether she was entitled to see the advice itself.

"I am pleased to say that I was able to clarify that matter and I am satisfied that I have now seen all of the information that falls within the scope of his request," she said.

"Having done so I am satisfied that the sole purpose of that information was to provide legal advice to the prime minister on the legality of military intervention in Iraq.

"The information I have seen does not include any other assistance that a lawyer might provide to a client, such as presentational or policy advice.

"I am satisfied, therefore, that all of the information contained in the documents drawn up by the attorney general that provided the prime minister with advice on the legality of military intervention in Iraq can reasonably be said to be covered by legal professional privilege."

Other criticisms

The ombudsman's report also reviewed other high profile complaints against the government.

One finding concluded that the government was within its rights to refuse to release a controversial National Audit Office report on the Al Yamamah arms contract.

The NAO report is believed to contain information on "kickbacks" paid during the course of the multi-billion pound deal with Saudi Arabia.

And the Ministry of Defence was also involved in a request for information on accidents and incidents involving nuclear weapons.

Following the ombudsman's intervention, Abraham concluded "that the public interest would best be served by disclosing the information and, following a series of meetings, MoD agreed".

The Department of Health also came under fire for failing to release information relating to the PowderJect smallpox vaccine contract.

Abraham recommended that almost all the information being sought should have been released.

The DoH eventually agreed to publish information that had already been put in the public domain through an NAO report, but refused to release other details.

As a result, the ombudsman criticised "the manner in which DoH had handled... [the] information requests and for their failure to engage effectively with her own investigation".

She added that consideration of the complaints had been "beset with delays and by a basic lack of  understanding... that does not augur well for the treatment of similar complaints under the forthcoming Freedom of Information legislation".

Summing up her latest reports, Abraham said: "Often there is a legitimate public interest in releasing the information.

"But the real difficulty lies in establishing whether or not that interest outweighs any harm which might result from disclosure.

"The code requires departments to be as open as possible about the information they hold.

"However, all too often their instinctive response is still to treat official information as non-disclosable without considering whether or not that is really the case."