NICOLA Sturgeon will hammer home her "Both Votes SNP" message in the final 24 hours of the election campaign today as jitters grow over her target of winning an overall Holyrood majority.

The SNP leader will address a rally in Glasgow city centre, when she will appeal for support on both the constituency and regional votes to "guarantee" the party's continued control over the Scottish Parliament.

Insiders voiced fears the SNP could fall short of winning a majority, especially if turn-out if low.

Read more: SNP must earn right to propose second indyref, says Nicola Sturgeon

They fear the party could increase its share of the vote compared with 2011 but still win fewer seats under Holyrood's complex semi-proportional system if, as expected, the independence-supporting Greens also do well.

Ms Sturgeon will rally supporters as Labour and the Conservatives step up their battle for second place.

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A poll, from Survation, yesterday put the two parties neck and neck, although Labour insiders remained confident they held a big enough lead to avoid a catastrophic slump into third place.

Kezia Dugdale, the Scottish Labour leader, issued figures showing the impact on public spending of her party's plan to increase income tax by 1p for most workers.

It claimed Glasgow would be £336million better off and Edinburgh £276million better off, compared with the SNP's more cautious tax proposals.

Read more: Nicola Sturgeon tries to steer election debate away from constitution amid fears over majority win

However, the crisis engulfing UK Labour leader Jeremy Corbyn continued to cast a shadow over her campaign.

Margaret Hodge was touted as a possible stalking horse challenger to Mr Corbyn's leadership, as he again struggled to close down claims of anti-Semitism within the party and experts predicted the loss of 300 council seats in England.

Ms Sturgeon yesterday sought to steer the election debate away from the constitution, following several days of angry criticism from opponents of her plans to push for a second referendum if support for independence grows.

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During a visit to Aberdeen, she promised to put jobs at the heart of her programme for a third term in government.

Senior colleagues also highlighted pledges on education and the health service.

With less than 24 hours until polls open, Ms Sturgeon will today campaign on Scotland's busiest shopping street, urging people to "ensure the re-election of an SNP government with an ambitious plan to keep Scotland moving forward".

She will add: "But the only way to guarantee that we are able to implement our vision for Scotland is to cast both votes for the SNP when you go to the polls on Thursday."

Read more: Second referendum while I am First Minister, says Nicola Sturgeon

Campaigning in Edinburgh South - one of a tiny handful of constituencies where Labour believes it has a slim chance of holding off the SNP - Ms Dugdale will say: "Tomorrow we can vote to stop the cuts.

"To make the next five years about the future rather than our past people have to use both their votes for Labour.

"A vote for anyone else will mean more cuts."

Also rallying supporters in Edinburgh, Scots Tory leader Ruth Davidson will repeat her pledge to provide strong opposition to a SNP government.

Claiming the Scottish Parliament has failed to live up to expectations, she will add: "The devolution generation deserves better."

SNP fears of failing to win a majority appeared to be unfounded, at least judging by the polls.

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Based on the latest Survation figures, one widely used seat prediction tool forecast the party to take 69 of Holyrood's 129 seats.

In a separate analysis, polling expert Chris Hanretty said it was 99 per cent certain the SNP would emerge with a majority.

He calculated the most likely outcome was for the party to take 70 seats.

In the battle for second, he said the Tories had a 25 per cent chance of beating Labour to become the main opposition party at Holyrood.

At Westminster, Jeremy Corbyn, facing continuing questions about his leadership, insisted: "I’m going nowhere."

Senior Labour backbencher Margaret Hodge was said to be considering an approach from disgruntled colleagues to launch a stalking horse challenge in a bid to spark a wider leadership contest.

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She was approached for a comment but did not reply.

Denouncing the media "obsession" with MPs plotting his downfall, Mr Corbyn said: "I don't know who these Labour MPs are but I would advise every member of the party, including our MPs, (to) get out there on the doorstep and campaign; we have two days to go."

His close shadow cabinet colleague Diane Abbott dismissed talk of a coup as "silly" and suggested if there were a leadership contest, there was no reason to believe Mr Corbyn would emulate his leadership poll and get 60 per cent of the vote.