The Scottish Conservatives are gaining ground on Labour in the fight to be Scotland's second largest party, according to a new opinion poll.

The Panelbase poll for The Sunday Times and Heart FM shows support for the Tories in Scotland, under leader Ruth Davidson, now stands at 17% in both the constituency and regional votes.

The figure is an increase of three percentage points in the constituency vote, and two percentage points in the regional vote compared with Panelbase's last survey in September.

In contrast, Labour have lost ground, dropping two points to 21% in the constituency vote, and down three points to 19% in the regional vote.

The poll of 1,054 voters, conducted between January 8 and 14, found support for the SNP at 50% for the constituency vote and 48% for the regional vote.

The Lib Dems recorded support of 6% and 7% for the constituency and regional polls respectively, while the Greens are on 3% for constituency, and 5% for regional.

The increase in support for the Tories comes as the parties enter the 100-day stretch before the May vote, and as the Commission for Competitive and Fair Taxation in Scotland, set up by the Tories, prepares to publish its findings.

The commission was established to examine how new income tax powers coming to Holyrood as part of the Scotland Bill can be used, as well as looking at the Scottish Parliament's existing powers.

According to the Scotland on Sunday newspaper, it is expected to advise that tax in Scotland should not be higher than other parts of the UK, and should be "lower where affordable".

Taxation is expected to become a key battleground in the election campaign.