The man at the centre of the Oxfam sex scandal had left an earlier charity job after it was claimed he was involved in sex parties with young women in Liberia.

Roland van Hauwermeiren, 68, had been working in the West African country when a colleague became so alarmed by his behaviour that she reported him to her superiors.

Amira Malik Miller, a former aid worker, claims she alerted her bosses at the British medical emergency relief charity Merlin after serving with van Hauwermeiren there in 2004.

She said he agreed to resign after an investigation found senior managers had been using local sex workers.

He was recruited by Oxfam to work on a project some two years later in Chad.

Last month he became embroiled in claims he had sex with vulnerable young women while working for Oxfam in Haiti in 2011, the year after an earthquake devastated the country.

After learning of the scandal engulfing Oxfam in which van Hauwermeiren was named, Ms Miller, who now works as a Swedish civil servant, said she was astonished he had managed to get to work for another charity.

“Oh my God, he’s been doing this for 14 years,” she told IRIN, a website covering humanitarian news. “He just goes around the system… from Liberia to Chad, to Haiti to Bangladesh. Someone should have checked properly.”