A former British army captain on Wednesday accused the Ministry of Defence of attempting to block publication of a book criticising the country's campaign in Afghanistan's restive Helmand province.

Doctor Mike Martin said he was commissioned by the MoD to research the conflict in Helmand, where British forces sustained the vast majority of their losses during the 13-year conflict.

But when he turned the doctorate study into a book, the ministry blocked its publication, saying its contents contravened the Official Secrets Act, he claimed.

Martin, 31, who served a total of 10 years in the army and the part-time territorial army, has now resigned his commission as a TA captain and plans to go ahead with releasing the book this month.

The book, "An Intimate War -- An Oral History of the Helmand Conflict 1978-2012", argues that commanders failed to understand the "tribal" nature of the conflict.

Martin said he told MoD officials of his plans to convert it into a book, with proceeds going to veterans' groups.

He said: "The PhD has already been published.

"Even before I was awarded it I sent it to various people in the army and the MoD. At the time I told them that I was going to be converting this into a book -- there's no difference in the content, just the style.

"I heard nothing until about February this year when they said 'you can't run it'."

He claimed he was told that the inclusion of material from WikiLeaks and "other classified material" would breach the Official Secrets Act.

Martin said: "I do believe the army needs to really look at how it does its business because there's been such an intelligence failure in Afghanistan.

"But I also believe you can't reform systems unless you are inside them, which I was."

- 'Publication not blocked' -

He denied the book was critical of the MoD as a body, but added: "it's critical of our ability to understand that type of conflict".

He also accused officials of trying to "protect the reputation" of Britain's US allies, who he claimed had made mistakes that destabilised the region before British forces even arrived.

But the MoD said Wednesday that claims of a "last-minute attempt" to block the book on secrecy grounds were "simply not the case".

It said it had funded Martin's doctorate studies on the conflict because it was interested in a "critical analysis of its role and in learning lessons for the future", but had not commissioned him to write a book.

In a blog posting, the MoD said that it was now satisfied the documents referred to in the book were in the public domain and so would not block its publication.

Martin was no longer bound by rules covering serving officers publishing books as he had resigned, the MoD said.

It went on: "Dr Martin has elected to resign his reserve commission and will publish the book as planned. The MoD has no objection to this and is not in any way attempting to prevent the book's publication.

"The army simply decided that it was inappropriate for a serving officer to publish a book that is so heavily critical of the army, the MoD and our allies. It respects the decision Dr Martin has taken."