Several members of McKinsey’s investment banking research team inappropriately took information from Coalition, their former employer, the consultancy has alleged to clients, days after firing the individuals and closing the unit pending a review of “various personnel matters”.

In a letter sent this week to senior executives at banks which used the CIB Insights service, two senior partners of the consultancy alleged that unnamed individuals had circumvented security measures at Coalition, the dominant provider of global investment banking research, to take information with them as they left to join McKinsey.

The letter, which was described to the Financial Times by someone familiar with its contents, adds that McKinsey’s investigation into the matter began at the request of Coalition, a financial services research business owned by Standard & Poor’s.

Two people familiar with the matter said that, after Coalition first alerted McKinsey, S&P chief executive Doug Peterson called Kevin Sneader, McKinsey’s global managing partner, to discuss its suspicion that the individuals concerned had taken information inappropriately.

Investment banks are highly sensitive about how their private data is used, and the letter emphasises that McKinsey had found no evidence that material non-public information had been misused, or that client data inappropriately obtained from Coalition had leaked or been used outside the CIB Insights team.

CIB Insights, which was set up in 2019, offered analytics and industry insights to major investment banks including Deutsche Bank, Credit Suisse and Morgan Stanley.

McKinsey said: “As a result of our review, we now believe several individuals violated McKinsey’s terms of employment and professional standards. While our clients’ information remains secure, we have taken immediate steps to terminate the employment of individuals implicated to date, suspend the CIB Insights products for the foreseeable future, and inform clients of the actions taken.”

Coalition and S&P declined to comment.

The McKinsey partners letter also emphasised that the firm had moved quickly in response, firing or suspending an undisclosed number of CIB Insights staff and “pausing” the unit’s work.

The letter suggests that some of the individuals under suspicion had made inappropriate efforts to poach their former colleagues, alleging that they had unauthorised communications with Coalition employees about the possibility of working for McKinsey.

It also alleges that former colleagues who were still at Coalition inappropriately transmitted information to individuals who had joined CIB Insights.

McKinsey launched CIB Insights as part of a strategy to add more data analytics to its consultancy services.

It poached several staff from Coalition, whose league tables many investment banks use in their marketing, but had only six active clients by the time McKinsey halted its work.

Both companies’ clients provided them with internal data to help them compile their analysis of costs, revenues, capital levels and headcount across different sections of the industry.

Coalition had revenues of £35m and a net profit of £11.4m in 2019, according to accounts filed with Companies House.