Scott Mann has told Government Ministers that millions of pounds of taxpayers' money must be "considered at every single step" when spent on foreign aid projects.
The statement came on Wednesday in International Development questions, where backbench MPs hold the department's Ministers to account.
Currently, 0.7% of GDP (£12bn) is spent on foreign aid, a Government commitment which was passed into law by the Coalition in 2015.
Shortly before Prime Minister's Questions, Scott asked for assurances from Ministers that all foreign aid was being spent on legitimate projects, adding that taxpayers' money be considered at every step.
Earlier that morning, the International Development Secretary, Priti Patel, had said in a national newspaper that she was going to make foreign aid more transparent so taxpayers' know their money is being spent on important and worthwhile causes.
You can watch the exchange in the House of Commons here.