Edward McKenzie-Green, 34, was already facing an internal inquiry because of “erratic and unprofessional behaviour” when he led a team of six to the disaster zone in 2011.
The Scot continued to steal from Oxfam on his return to the UK before resigning with a £29,000 “golden handshake” in November 2011.
Investigators then discovered he had filed 17 bogus invoices from two companies – Loss Prevention Associates and Solutions de Recherche Intelligence – over the previous nine months, totalling £64,612.58.
Some of the payments went into an account belonging to his father, Edward Green, 62, from Cumbernauld, Lanarkshire. Mr Green was cleared of concealing criminal property between 1 February and 1 December 2011.
Investigators contacted the supposed head of Loss Prevention Associates, Keith Prowse, for an explanation of the invoices for “intelligence investigation”, “surveillance equipment” and “Haiti confidential” only to find Mr Prowse was McKenzie-Green.
McKenzie-Green, who had an annual budget of £250,000, was abusing antidepressants and an anabolic steroid designed for animals at the time of his thefts.
His barrister Matthew Sherrat told the court his client had a serious addiction to prescription medicine, his marriage was failing and he suffered a breakdown, requiring him to be treated in a psychiatric hospital for a month for paranoia.
Mr Sherrat said: “He was putting money aside effectively in the expectation of losing his job.”
His wife has since left him, taking their child.
Senior staff already had concerns when he was asked to lead a team of counter-fraud investigators in Haiti in July 2011.
Prosecutor Adam King said: “He had demonstrated an erratic, disorganised and even combative approach to his work.
“Internal investigations had begun six months earlier in December 2010.”
Because of the concerns, McKenzie-Green’s boss went out to Haiti to supervise the first few days of the visit. Several members of staff were dismissed for misconduct in Haiti as a result of the investigation but McKenzie-Green continued to behave in an “erratic, unprofessional and untrustworthy” manner.
On his return to the UK, he was reported to Oxfam’s human resources and disciplinary proceedings were initiated.
Mr King added: “He was offered [the option of] resignation but he refused it.”
Eventually he did resign, in November 2011, with a golden handshake, after he signed a declaration that he had not done anything that might constitute gross misconduct. Then the fake invoices were discovered.
He was arrested in April 2012 and denied any wrongdoing. In July 2013, he alleged “corruption and conspiracy amongst senior staff at Oxfam”, said Mr King. He finally pleaded guilty in March after police found a credit card application for “Lord Prowse” with “Sir Eddie McKenzie-Green” as the additional cardholder.
McKenzie-Green, of Chipping Norton, Oxfordshire, admitted fraud. A charge of stealing a laptop was dropped.
Jailing him for two years and five months at the Old Bailey yesterday, Judge Wendy Joseph QC said: “The consequences of your conduct are grave indeed. You have taken from those, who desperately need it, substantial sums.
“Worse, you have undermined the public confidence in a charitable institution. You were head of a department set up to counter fraud. This was a profound abuse of trust.”
Oxfam’s new head of counter-fraud, Phillip Dunn, said: “Oxfam is trying to become a world leader in counter-fraud investigation and to have the head of counter- fraud contribute to that is immeasurably damaging.”