Spain's caretaker government says it will take legal action against the parliament of Catalonia after pro-independence parties governing the region defied Spain's Constitutional Court by approving a resolution to press ahead with secession.

The resolution was approved Wednesday in the regional parliament in Barcelona by the "Together for Yes" group and its anti-capitalist coalition partner CUP, despite protests from opposition parties that it was illegal.

The motion was another step in the regional government's road map for independence by 2017 that was approved in 2015 but ruled as unconstitutional by Spain's top court.

The Spanish government said it had contacted the nation's main opposition parties to inform them that it would take legal action to block the process.

Catalonia accounts for nearly a fifth of Spain's economic output.