Thomas Cook posted a net loss of £605 million ($942 million) for the six months to 31 March, compared with a net loss of £201 million in the same period last year.
The company's underlying loss before tax amounted to £328 million for the reporting period.
Its revenue for the period increased by 2.62% to £3.52 billion, compared with £3.43 billion in the previous year.
The group's loss from operations amounted to £643 million, which includes £300 million of non-cash goodwill impairments.
The free cash outflow for the period was £522 million - an increase of £267 million on the comparable period last year - driven by a £97 million higher seasonal operating loss and a £215 million increase in working capital outflow.
Commenting after the results were announced, interim chief executive Sam Weihagen speculated that the company may benefit from a surge in bookings to Greece if the troubled country leaves the Eurozone.
He argued that rapid currency devaluation - which analysts widely expect to accompany any return to the drachma - would make Greek holidays better value for British tourists.
Thomas Cook shares closed down 7.38% at 18.76p today (31 May), partially recovering from its session lows of 17.25p.