Its report underlines the difficulty of achieving two key promises of President Muhammadu Buhari’s 2015 election campaign: tackling endemic corruption and defeating an insurgency that has claimed over 20,000 lives and displaced millions.

“Corrupt military officials have been able to benefit from the conflict through the creation of fake defence contracts, the proceeds of which are often laundered abroad in the UK, U.S. and elsewhere,” the watchdog said in a statement.

Last year, Nigeria’s vice president said around $15 billion had been stolen from the public purse under the previous government through fraudulent arms procurement deals.

Transparency International said this had left the military “without vital equipment, insufficiently trained, low in morale and under-resourced”.

“This has crippled the Nigerian military in fighting an aggressive ideologically inspired enemy such as Boko Haram,” the watchdog said, pointing to cases of soldiers taking on the militants without ammunition or fuel.

A defence spokesman said the allegations were false for the current crop of military officers.

“A lot has been done to train, boost troops’ morale and procure vital equipment through due process,” said Major General John Enenche, adding that the military “will continue to get better with the right kind of leadership that we have today”.

The military says it has recaptured much of the territory claimed by Boko Haram since the conflict began in 2009. But the reclaimed areas are often razed towns, or islands of relative safety and highways connecting them to larger cities.

Much of the territory away from the roads is still dangerous, and Boko Haram attacks remain frequent.

The report also said countries such as the United States could encourage defence reform by withholding arms, such as the planned sale of up to a dozen Super Tucano A-29 aircraft to help the fight against Boko Haram.

Transparency International said Nigeria should make its defence budget and procurement systems more transparent to ensure that contracts were not inflated, or given to shell companies to conceal the true beneficiary.