Troubled tour operator Thomas Cook has confirmed group chief executive Manny Fontenla-Novoa is to step down with immediate effect.

Sam Weihagen, currently deputy chief executive, will take on the role on an interim basis while a search process gets underway to identify a permanent successor.

Thomas Cook released its quarterly results earlier showing profits fell to £20 million for the three months to June 30th 2011 from £26 million last year.

A weak performance in the UK was to blame for the fall, Thomas Cook said in a statement.

Following the departure of Manny Fontenla-Novoa Thomas Cook chairman, Michael Beckett, said: “The board would like to thank Manny for his contribution to the group. 

“He leaves with our very best wishes for the future.

“In Sam Weihagen, we have a highly successful and experienced executive and the Board has every confidence in his ability.”

Thomas Cook recently launched a ”fundamental review of its activities after issuing a profit warning, while Morgan Stanley has warned a merger with rival TUI may be the only route to survival for the tour operator.

Thomas Cook confirmed trading was in line with expectations, with the tour operator expecting to make £320 million profit for financial 2011.

The Competition Commission provisionally cleared the merger of Thomas Cook’s high street retail travel and foreign exchange network with The Co-operative Group and the Midlands Co-operative earlier this month.

The deal will create the UK’s largest multi-channel travel retailer.