Catalonia's pro-independence parties could win the most seats in next week's knife-edge regional elections but fall short of an absolute majority in parliament, according to the final polls before the vote.

Five new polls published on Friday put the three separatist lists on course to win 63 to 69 seats in the 135-seat parliament on December 21, with 68 seats needed to control the assembly. They won 72 seats in the 2015 election.

The pro-unity parties were expected to take between 56 and 63 seats, with the leftist Catalunya en Comu party, which is anti-independence but supports holding a legal referendum, potentially holding the balance of power with eight to 11 seats.

Two of the polling firms projected that the separatist parties could retain the absolute majority of the outgoing regional parliament, which was dissolved by Madrid after the Catalan assembly unilaterally declared independence on October 27.

The region is currently under direct rule from the national government in Madrid, which called new elections after a banned independence referendum led to Spain's worst political crisis in a generation.

A poll by the Gesop Institute published in newspaper El Periodico de Catalunya said the pro-independence parties will win 66 to 69 seats, and another by polling firm Sigma Dos published in El Mundo put them on 64 to 69 seats.

Three of the polls had the leftist, separatist ERC party favourite to win the most seats, with the other two polls predicting pro-unity centre-right Ciudadanos will come out on top.

ERC — the party of ousted Catalan president Carles Puigdemont's former vice-president Oriol Junqueras — was expected to win between 29 and 35 seats.

Puigdemont's Together for Catalonia list, which includes members of his PDeCAT party, would win between 22 to 30 seats, the polls indicated, with the far-left CUP taking six to nine.

For the pro-unity parties, the polls said Ciudadanos would have 27 to 36 seats, followed by the Socialist party with 19 to 24 and the conservative Popular Party of Spanish Prime Minister Mariano Rajoy on five to eight.