Laying out the SNP's blueprint, the party's Westminster leader said the fiscal injection needed to be at least the equivalent of 5 per cent of the UK's GDP.
Writing for The Scotland on Sunday, the Ross, Skye and Lochaber MP urged the Chancellor Rishi Sunak to invest after a year that UK employment shrink 9.9 per cent.
He said: “With the UK Budget in ten days time, the first priority must be to ensure that people, businesses and public services get the immediate support they need to get to the other side of this crisis.
“Above all, this should be a budget that invests in growth and meets the huge scale of the challenge we face.
"That means a major fiscal stimulus of at least £98 billion, the equivalent of five per cent of GDP, to protect people’s livelihoods and lay the foundations of an investment-led recovery.
“UK unemployment has risen to 5 per cent, redundancies are at a record high, and there are over 800,000 fewer people in work.
"We must not have a repeat of the Thatcher years - when the Tories left people on the scrap heap and caused lasting scars on our communities by failing to act.”
The SNP’s leader in Westminster accused Mr Sunak of being “nostalgic” for the era of austerity, and claimed he was putting Scotland’s future at risk.
The Chancellor has repeatedly insisted he will do “whatever it takes” to support people, but he has now been labelled a threat to the economic recovery.
Mr Blackford said: “At the very moment when the economy needs maximum investment, the Chancellor is threatening Scotland’s recovery with a return to Tory austerity cuts.
"The fact that the Tories are even considering a public sector pay freeze, and cuts to Universal Credit, show they are returning to type and have failed to learn the lessons of the pandemic or the last financial crisis.
“It’s been clear for some time that the Chancellor is getting nostalgic for the return of conservative cuts - he’s desperate to get back to the Tory austerity agenda.
"That fundamental chasm between the cruel choices the Tories are threatening to impose and the economic choices Scotland now needs, speak to a wider reality and a defining choice for our people in the time ahead.”
Mr Blackford has now urged Mr Sunak to change course, and ensure people, businesses and public services get immediate support.
He pointed to the ongoing refusal to extend the Universal Credit uplift, the delays over extending the furlough scheme, and a lack of support for the self-employed.
The 59-year-old explained: “The SNP has repeatedly raised the plight of the three million people who have been completely excluded from covid support, including many self-employed and freelance workers who haven’t been given any help by Westminster.
"After a year of excuses, the Chancellor must finally act.
“There must also be increased support for the growing number of unemployed and low income families who are seeing their household budgets hit as a result of the downturn.
"This must include a full U-turn on cruel Tory plans to cut Universal Credit. Instead of taking money away from families, the £20 uplift must be made permanent and extended to legacy benefits.”
A Treasury spokesperson said: “The UK government has protected nearly a million jobs and thousands of businesses in Scotland since the start of the pandemic.
“And just this week the Treasury provided the Scottish Government with an additional £1.1 billion, enabling them to support people, businesses and public services affected by coronavirus.
“At the Budget the Chancellor will set out the next stage of our plan to protect and create jobs in all corners of the UK.”