"Companies may have skeletons in the cupboard, but do not want to stick their heads above the parapet," said one engineer.
"If the impact of a company admitting to past mistakes is to put the company up for execution, nobody will face up to corruption," another added.
One delegate pointed out that according to Transparency International, construction is rated as the most corrupt sector in Africa, worth around £46bn per year.
Delegates spoke frankly about the issue in the Chatham House Rule meeting in which views are not attributed, and said that the only way for companies to ensure ethical behaviour would be to walk away from countries where corrupt practice is common.
"We used to operate a great deal in Africa. Sadly, now we do not," said one.