KEZIA Dugdale has received a boost in her fight to ensure Labour remain the main opposition party at Holyrood, after a new poll found that she is on course to hold off Ruth Davidson's Tories.

The results of the TNS survey, published this morning, also reported a decline in support for the SNP although Nicola Sturgeon's party still enjoys a huge lead over its opponents and remains in line to win another majority.

In the constituency section, the nationalists are polling at 52 per cent, a drop of four points in one month and eight since February. Labour recorded 22 per cent support, up three, with the Conservatives up two to 17 and the Liberal Democrats up one to seven.

On the regional list vote, the SNP are on 45 per cent, down two, with Labour up one to 22 but the Tories closing the gap, gaining three per cent in a month leaving the party on 18 per cent support. The LibDems are down one to five and would be replaced by the Greens, currently enjoying eight per cent of support, as the parliament's fourth party.

The Herald:

A narrow lead over the Conservatives will be met with relief within Labour, coming the day after an Ipsos-MORI poll for STV found that the party was set to be replaced as Holyrood's second largest party.

According to the ScotlandVotes seat predictor, if the result was repeated next week it would leave the SNP on 70 seats, with the party coming close to sweeping the board of constituencies but claiming just two regional list seats.

Labour would return 27 MSPs, with the Tories recording its highest tally ever with 21. The Greens would return eight MSPs, in what would also be the party's best ever result. The LibDems would be reduced to just three.

The Herald: Picture: COLIN TEMPLETON03/04/15 Green party MSP Patrick Harvie.Picture: COLIN TEMPLETON (41556838)

Tom Costley, Head of TNS Scotland said: "As the various parties are building up to the final week of campaigning, have some of the criticisms of the SNP’s performance as the Scottish Government had an impact on the electorate? Or is the downturn in the SNP vote in both the constituency and regional list a reaction to the concerns being expressed by some commentators of the dangers of one party being so dominant within Holyrood?

"Despite the decline in SNP support over the last two months, a 52 per cent share of the constituency vote would still represent an increase from the 45 per cent they achieved in 2011. There is no denying that the SNP continues to be in a very dominant position.

"While Labour and Conservatives have made some progress in the last few months, both are likely to be disappointed when the final results are announced. The polls suggest the Labour party is still struggling to match the share of the vote they achieved in 2011 let alone begin a recovery. The Conservative Party do not yet appear to be in a position which will see them replacing Labour as the official opposition."

The face-to-face survey of 1,035 adults aged 16 and over in Scotland also shows that the proportion claiming they are certain to vote has remained steady at 67 per cent for the third month in a row.

Mr Costley added: "If a turnout of this level is seen on 5th May it will be significantly higher than the 50 per cent turnout in 2011, and a further indication of greater engagement with politics in Scotland following the referendum."

Scottish voters aged 18 and over were also asked about how they intended to cast their ballots in the EU referendum on June 23. Almost half of voters, 48 per cent, said they would vote to remain in the EU with 21 per cent saying they wanted to leave and 31 per cent saying they didn't know.

The proportion of undecided voters is particularly high among women, with 41 per cent unsure compared to one in five men. Three quarters claim that they are ‘certain to vote’ in the referendum, up from 72 per cent last month.