Scottish Labour was the last of Holyrood's main parties to launch its manifesto, though for leader Kezia Dugdale the timing could perhaps have been better.

As she unveiled the policy document in Edinburgh, a new poll showed her ranking with voters had slumped by 16 points in two months.

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The Ipsos Mori poll gave Ms Dugdale a net satisfaction rating of -11 - a score which is down from +5 in February - while her main rival, Scottish Conservative leader Ruth Davidson, saw her rating increase by seven points to +15.

Labour are locked in a contest with the Tories to see who will form the official opposition to the SNP after the May 5 election.

If the party slips behind the Conservatives to become the third largest in the Scottish Parliament, it would be its worst-ever Holyrood result.

But a defiant Ms Dugdale said even if that happens she would continue to lead her party.

''The problems with the Labour Party didn't happen overnight and they're not going to be fixed overnight," Ms Dugdale insisted

''I said when I put my name forward for the leadership of the party that I have a plan to turn things round and I believe I have delivered on that plan.''

She argued Labour is the ''only party offering an alternative to austerity'' as she put forward the manifesto, with its plans for tax rises to prevent cuts to local services and raise money for education.

But to add to Labour's woes, research by academics found its voters to be considerably less left-wing than SNP supporters.

The study by Strathclyde University found 44% of Labour supporters backed policies deemed left-wing while nearly 73% of SNP supporters gave left-wing responses.

Meanwhile, far-left party Solidarity, founded by former MSP Tommy Sheridan after a bitter split with the Scottish Socialists, published its manifesto this week, with a pledge to bring forward legislation to bring about a second independence referendum in two years.

Mr Sheridan, who served a jail sentence for perjury, urged voters to ''punish'' the pro-UK parties for the ''despicable lies'' told in the run-up to the previous referendum in September 2014.

While SNP leader Nicola Sturgeon has said she would "very much" like the chance to hold a second ballot on Scotland's future, she insists nationalists ''first have to earn the right to propose it'' by convincing a majority of Scots to back it.

Ms Sturgeon and her party maintained their comfortable lead in opinion polls but business leaders have raise concerns about the party's rates policy.

In a joint statement released a week before the election, Scottish Chambers of Commerce, Scottish Engineering, Scottish Tourism Alliance, Scottish Property Federation and the Scottish Retail Consortium said they feared companies would continue paying higher rates than those south of the border under another SNP government.

The SNP also faced questions about the choice of slogan for its latest billboard campaign, which saw posters go up across Scotland featuring Ms Sturgeon alongside the words "'Don't just hope for a better Scotland. Vote for one''.

The message echoed one from Conservative Margaret Thatcher's successful election campaign in 1979 which showed the "Iron Lady" telling voters: ''Don't just hope for a better life. Vote for one.''

Scottish Labour deputy leader and campaign director Alex Rowley commented: ''We knew the SNP under Nicola Sturgeon had ditched the left-wing rhetoric but we didn't expect them to start stealing Thatcher's lines."

Ms Sturgeon said: "'If Labour are saying that it just shows beyond any doubt how desperate Labour are."