Inequality will "last until doomsday" under the SNP because Nicola Sturgeon is obsessed with waging "a war against the Union" rather than improving the lives of ordinary Scots, Gordon Brown has said.
Mr Brown, a former Labour prime minister, said nationalists would not tackle the "crime" of child poverty, which the First Minister has insisted will be a priority if she is re-elected, because in reality they spend "all their waking hours trying to change our borders".
Scottish Labour deployed its biggest name on the eve of the Holyrood elections at a pre-election "drive-in" rally in a car park in Glasgow Southside, where Anas Sarwar is going head-to-head with Ms Sturgeon.
In a passionate speech, Mr Brown – seen as having played an influential role in defeating the separatists at the 2014 referendum – repeatedly attacked the SNP’s record in government.
He said the party had been unable to address problem with mental health services, NHS waiting lists, social care and plummeting standards in education over their 14 years in government, so would "never solve the problems now" amid the challenges of the Covid pandemic.
"We want to end child poverty, the SNP want to end the United Kingdom," Mr Brown, 70, told Labour activists. "They spend all their waking hours trying to change our borders, we spend all our waking hours trying to change society.
"They're fighting a war against the Union, we're fighting a war against poverty, deprivation, ill health, illiteracy. I tell you this – given their obsession with independence, economic inequality and social injustice would last until doomsday if the SNP is all that confronts it."
Mr Sarwar has won plaudits for running an upbeat campaign and has seen his personal approval ratings rise significantly since he took over as the Scottish Labour leader in February. However, most polls have shown support draining away from Labour in the final days of the campaign and predict the Tories will comfortably remain Holyrood's second-largest party.
Mr Brown acknowledged that Labour – which according to most surveys is set to lose seats and record its worst-ever result in a Holyrood vote – was "fighting against the odds" in the election.
He also launched an attack on Boris Johnson and the Conservatives, as Labour and the Tories fight each other for pro-UK voters' regional ballots, highlighting the controversy over the funding of Mr Johnson's Downing Street flat refurbishment and hitting out at the Prime Minister's claim that the UK's successful vaccine programme was down to "capitalism" and "greed".
"It's not just the undisclosed gifts," Mr Brown said. "It's not just the unreported conflicts of interests. It's not just the undeclared lobbying. It's not just the behaviour of this government that angers me. It's their values.
"It is not greed and capitalism that's winning the war against this [virus]. It's the NHS, and the people of this country. It’s sharing, caring, cooperation, solidarity. These are the values that we believe in. I tell you, Scotland is better than Nicola Sturgeon's SNP and Britain is better than Boris Johnson's Conservatives."
Shirley-Anne Somerville, an SNP minister, said: "The only thing people in Scotland want to hear from Gordon Brown is an apology for his campaigning so vocally in 2014 to keep key powers over poverty in the hands of the Tories at Westminster.
"As a result, we've had years of Tory austerity and welfare cuts inflicted on us, we've been dragged out of the EU against our will and now we have Boris Johnson as Prime Minister.
"Child poverty in Scotland – while still too high – is significantly lower than in other parts of the UK. But as long as people like Gordon Brown are campaigning to leave the key levers in the hands of the Tories at Westminster, we'll be fighting issues like child poverty with one hand tied behind our backs."
Mr Sarwar told the rally that the election was "part of a journey to having a Labour First Minister and Labour government".
He later told journalists: "I am building the credible alternative to Nicola Sturgeon and the SNP. Opposing them is one thing, that's all the Tories can do. I want to be the alternative to them. I want to be First Minister, I want to lead a Labour Scottish Government."
However, the Scottish Tories highlighted the support of Tom Harris, the former Scottish Labour MP who revealed he had reluctantly voted Conservative with his second ballot because he believed tactical voting would deliver more pro-UK MSPs.