Pro-independence parties are on track to win a slim majority of seats in Catalonia's parliament in an election later this month, a poll has indicated.

Such a victory would potentially pave the way for the wealthy region to declare independence from Spain.

The poll of 3,000 Catalan voters by the state-run Sociological Research Centre (CIS) found the main pro-independence movement Junts pel Si would win 38 per cent of the vote, or 60-61 seats in the 135-seat Catalan parliament.

Together with a predicted eight seats for the left-wing, pro-independence party CUP, it would give those who favour breaking away from Spain a very slim majority with 68 or 69 seats.

Pro-independence parties are portraying the regional election as a proxy vote on independence and have said winning a majority of seats, and not necessarily of votes, would allow them to launch a "road map" to secession within 18 months.