Ministers must do more to tackle the "appalling conduct" of some international aid contractors used to deliver UK assistance to some of the world's poorest people, MPs have warned.
The Commons International Development Committee said there were "fundamental flaws" in the working practices of some of the organisations responsible for handling tens of millions of pounds of taxpayers' money.
Amid allegations of "excessive profiteering" and "unethical conduct", the committee said the Department for International Development (Dfid) needed to take a "more robust approach" towards regulating the sector.
Much of the concern has centred on the activities of Adam Smith International (ASI) which was strongly criticised in an earlier report by the committee for trying to manipulate evidence to its inquiry.
The firm - which reportedly received at least £300 million in public funds over the past five years - recently announced its four founders were leaving in a complete restructuring of its top team.
However, the committee warned that ASI should not be treated as an "isolated case" and that reports had suggested the conduct of other contractors was "completely unacceptable".
"We are also greatly concerned about the appalling conduct of some contractors who have behaved in a way that is entirely misaligned with the department's purpose," the committee said.
"We have heard that there are fundamental flaws in the working practices of some organisations.
"The allegations made of ASI should not be approached as an isolated incident by Dfid, but as evidence that there is something inherently wrong with the culture in certain organisations.
"Dfid needs to take a more robust approach in creating regulations and incentives that shape the sector so that it operates to the highest ethical standards."
Dfid said International Development Secretary Priti Patel had already launched a review of the department's work with suppliers with a view to achieving "root and branch" reform based on principles of accountability and transparency.
"The Secretary of State has been crystal clear that she expects all suppliers to deliver results for the world's poorest, provide value for taxpayers' money and that she will not tolerate anything less," a spokesman said.