TUI’s finance chief Paul Bowtell is stepping down after an accounting error led to £117m of debt that the tour operator will now have to write off.

Europe’s largest travel operator blamed the integration of accounting systems following the 2007 merger of the First Choice Travel with the tourism division of Germany’s Tui AG.

Tui shares fell 6.6 percent on the news, dropping 15.1p to 215.3p, after it announced write-offs of £117m in its UK tour operator business.

TUI Travel said the debts had “arisen as a result of failures to reconcile balances adequately in legacy systems”.

The company said in a statement that Bowtell’s decision to resign followed discussions with the firm’s chief executive Peter Long.

Peter Long said: “Paul is behaving honourably and I am disappointed that he will be leaving the group.

“He is one of the most capable chief financial officers I know.”

Tui declined to indicate whether Bowtell, 42, will be getting a payoff, saying “any terms are under discussion”. He previously worked for First Choice as finance director.

Separately, Tui reported a strong increase in winter holiday bookings, with bookings from the UK up 6 percent as at October 17 compared with the same period last year.

The Nordic region saw the strongest upturn in demand, with bookings up 32 percent. Germany and France saw increases of 10 and 13 percent respectively.