Turmoil in some popular holiday spots in the Middle East and North Africa and later travel restrictions helped push the tour company to an operating loss of £165.8m (Dh991.2m) in the six months to the end of March, compared with a £130m loss in the same period last year, it said yesterday.
"It is hard at this point, given the continued unrest in the region, to estimate the likely financial impact for the full year," said Paul Hollingworth, the group chief financial officer of Thomas Cook.
The losses from the turmoil comprised about £5m in repatriation costs and £17m in lost bookings. Of the cancellations, 120,000 were for Egypt and 40,000 for Tunisia.
"Clearly the situation there has not returned to normal and while we are operating holiday programmes to Egypt and Tunisia, these are at reduced levels and load factors are not yet where we want them," said Mr Hollingworth.
The company is estimating it will suffer a loss of about £35m in the second half - £15m higher than previously forecast - because of political unrest in the region.
"At this stage, we estimate that our programme to Egypt, Tunisia and Morocco for summer will operate at approximately 60 per cent of the level originally planned, but this could change if the political situation does not improve," the tour operator said.
"The ongoing unrest in Libya and other countries in the region is weighing on consumer demand and recovery is slower than expected, despite the significant bed-rate reductions we have achieved."
The company said it was trying to mitigate the impact of the regional upheaval on its business by directing tourists to destinations such as Turkey and Spain instead.
"It will take several years for travel and tourism in Egypt to recover to 2010 levels after the expected drop of 18 per cent in international arrivals in 2011, and subsequent 20 per cent fall in incoming receipts," said Nadejda Popova, a travel and tourism industry analyst at Euromonitor International.