Five senior IT professionals have left the company to join the IT department of credit rating agency Standard & Poor's (S&P) over the past two years.
Although poaching is common in the financial services industry, the defections are a blow to the retailer, which prides itself on a staff retention rate far above the industry average.
The staff movement has also prompted John Lewis to review its salary structure to ensure that its rates are competitive with rival employers, amid the IT skills shortage.
The defections began when Christopher Down, head of central systems at John Lewis, which has about 550 IT staff, left to become regional practice leader responsible for IT at S&P.
Down has built up S&P's IT department, based in London's Finsbury Circus, from 17 to 50 as the company expands its European operations.
S&P is understood to have offered new recruits salaries which are significantly higher than the pay rates offered by John Lewis. One section head and several team leaders are among those to have joined S&P from the retailer.
Other John Lewis staff have made approaches to S&P, but have not been offered work.
"Down was given a war chest of cash to recruit an IT department, which he did. But a number of our people turned it down. They decided they had a better future with John Lewis and were a bit wary of cheque-book recruitment," said one senior IT professional at the retailer.
John Lewis said it conducts regular audits of IT salaries.
Recruitment experts said that although poaching was widespread in financial services, it often went unreported.
"Poaching is very common in financial services, especially if people in management positions go. A senior person leaves and other people go with them. I think it is more common than most people let on," said Richard Moule, senior manager at anti-headhunting advisory firm, David Charles.
Moule said it was not unusual for companies to monitor e-mails to protect staff from approaches from headhunters.