The leader of Catalonia Carles Puigdemont has accused King Felipe VI of following Spain's central government's "catastrophic" policies towards the region.
The Catalan president called the central government "irresponsible" for not accepting mediation in the political crisis.
Mr Puigdemont's government is considering when it will declare independence from Spain in the wake of a disputed referendum which triggered the country's worst national crisis in decades.
He has said an independence declaration will come within a few days, but Spain, which declared Sunday's referendum illegal and invalid, is bitterly opposed to any such move.
In a televised speech late on Wednesday, Mr Puigdemont condemned violence by police who tried to halt Sunday's referendum.
"We held the referendum amid an unprecedented repression and in the following days we will show our best face to apply the results of the referendum," he said.
The separatist leader told the king: "You have disappointed many Catalans."