By Andrew Edgecliffe-Johnson in New York

McKinsey & Co will not know for 20 years what damage the Galleon insider trading scandal has done to its brand, the head of the management consultancy has said, describing the case – in which two of its senior executives were caught up – as ?incredibly distressing and embarrassing?.

Clients had been very supportive, Dominic Barton, McKinsey?s global managing director, said in his fullest public comments on the affair, pledging to make the organisation stronger.

?I feel like some turpentine was thrown on the hood of the car,? Mr Barton told the Financial Times when asked about the state of a brand that has stood for trusted high-level advice and strict client confidentiality. ?I wish I could say it changed next week or in six months . . . I really think it will be in the 10 to 20-year time frame we?ll know.?

Anil Kumar, a former McKinsey partner, has pleaded guilty to charges of providing confidential information to Raj Rajaratnam, the ex-head of the Galleon Group hedge fund who was found guilty in May in a landmark insider trading case.

Rajat Gupta, a former head of McKinsey, has been charged with civil violations by the Securities and Exchange Commission but denies wrongdoing.

The case had prompted deep reflection about what went awry and dented the pride of an institution that had sometimes been ?arrogant?, Mr Barton said. He added, however, that ?it hasn?t affected our work at all?.

McKinsey had instituted a rigorous external review of its values and practices, prompting changes to policies, compliance and training, he said, but now ?felt good about where our standards are? in comparison to other professional firms.

?We?re looking at what people will say in McKinsey 20 years from now about how this generation responded,? he said.

Mr Barton said there was a wider drop in trust in business since the global financial crisis, which would require capitalism to adopt a longer-term perspective, freeing executives from running their companies to hit quarterly earnings targets.

McKinsey was looking at how to change asset managers? incentives and methods of measuring performance to encourage a longer-term approach from investors, he said.

? The Financial Times Limited 2011