Anas Sarwar has said Scottish Conservatives are trying to “con” voters at the Holyrood elections.
The Scottish Labour leader told Times Radio a vote for the Tories would be a “get out of jail free card” for Nicola Sturgeon, but admitted his party had an uphill struggle.
It comes as he revealed Labour’s top 50 pledges to deliver a national recovery.
Speaking on the G&T show, he rejected the idea that only a vote for the Scottish Conservatives could stop a second independence referendum.
He said: “They’re trying to con the Scottish people. So what they’re saying is to stop the SNP and to save the union, you need to vote for the Conservative Party.
“But in actual fact, the biggest threat to the UK is in many ways the Conservatives and they are the best get of jail free card for Nicola Sturgeon.
“Don’t be conned by the Tory message about a second vote.
“If you want to focus on what unites – not what divides us – if you want to focus on a national recovery, you need to use your second vote for Labour.”
Sarwar added: “The glory days do seem very, very far away and we have had 20 years of decline in the Labour vote.
“I’m not projecting I’m some kind of superhero that’s going to turn our 14% vote share in eight weeks, when I took over leadership, into us being in government.
“Of course that’s for the people of Scotland to decide over the course of the next five days.
“I want to take us on a journey for relevance, to credible opposition, to a credible alternative.
“That’s what I’m doing over the course of this campaign.”
Meanwhile, the party’s top 50 pledges are to be focused on five recovery plans covering jobs, the NHS, education, climate change and communities, setting out a positive vision for rebuilding Scotland.
To develop the skills for economic recovery and the green jobs of the future, Labour has set out a guarantee for everyone on furlough to access training to develop their skills.