Ride-hailing giant Uber lost more than 1.1 billion euros in the first half of this year, according to reports.
It is being put down to subsidies given to drivers, sources suggest.
Uber, now valued at roughly 61 billion euros, lost almost 1.8 billion in the whole of 2015.
Rapidly expanding tech start-ups such as Uber have faced opposition from some unions and longer-established competitors around the world.
In London, drivers of traditional black cabs have held a series of protests in the capital.