NEW YORK (AFP) - Credit rating agencies came under fire for their role in the global financial crisis Wednesday, as senior industry figures including mega-investor Warren Buffett faced a grilling from US investigators. Answering allegations that ratings firms helped propel the sale of risky investments which poisoned the global financial system, some senior officials from Moodys Investor Service admitted mistakes were made, but denied any wrongdoing. The powerful big three raters Moodys, Standard & Poors and Fitch are accused of blithely awarding complex mortgage-backed securities their lucrative AAA investment ratings simply to net more business. These top ratings are often seen as a seal of approval by investors and a sign that a company, country or debtor will pay back borrowed cash on time and in full. Raymond McDaniel, Moodys chief executive, told a Congress-appointed independent panel it was deeply disappointing that the firm failed to sniff out how risky mortgage-backed investments were, but said steps had been taken to improve the system. Moodys is certainly not satisfied with the performance of these ratings, he said in prepared remarks. There has been an intense level of self evaluation within our organization. The ratings agencies have come under fire from US lawmakers who are putting the final touches to financial reforms that would see stiffer curbs on how the firms do business. Criticism has focused on the fact that agencies are paid by the same firms they rate. Eric Kolchinsky, a whistleblower who once worked for Moodys, said the industry was unregulated and given a blank check to pursue profits over sound assessments. Rating agencies faced the age-old and pedestrian conflict between long-term product quality and short-term profits. They chose the latter, Kolchinsky said in prepared testimony. He also accused Moodys of lying about the influence that banks which packaged and sold mortgage-backed securities had over the ratings process. Banker requests to keep certain analysts off of their deals were granted, he said. But Moodys CEO McDaniel argued conflicts are inherent in any business model and that criticism of the current model ignores the fact that ratings in other sectors, which have operated under the issuer-pays model for four decades, have performed well. He said that some proposals to regulate the market would likely have a positive impact, but that other measures were contradictory. Billionaire investor Warren Buffett, who owns a major stake in Moodys, was expected to testify later in the day.