An opinion poll published by the El Periodico newspaper on Sunday showed a new poll would probably have results similar to the last, in 2015, when a coalition of pro-independence parties formed a minority government.
Other opinion polls have shown Catalonia is almost evenly split between pro- and anti-independence supporters.
Meanwhile Catalonia's main secessionist groups have called for widespread civil disobedience. They also instructed civil servants not to obey orders from Madrid and respond with peaceful resistance.
Spain's government said it was not planning to make any arrests, but it is unclear how it will proceed if the current regional administration staff refuse to leave their offices.