People Before Profit has launched its alternative budget ahead of the Government's Budget 2021 tomorrow.
The party has based the figures on a 'Zero-Covid Strategy' for the country.
Speaking at the launch outside the Department for Health, TD Richard Boyd Barrett said funding of that strategy was central to the party's plan.
He said: "We will not be able to protect the population, the livelihoods of workers and the future of our society unless we get on top of the Covid-19 crisis which we think the government strategy to date has failed to do."
The party said it would spend just under €1bn on mass testing, tracking and tracing the coronavirus.
It would double the weekly Covid-19 tests to 200,000 at a cost of €828m, while also increasing funding for research and development into new ways of testing and tracing by €100m and investing another €35m into public health teams for tracking down the virus.
The plan outlines how, in order for a Zero-Covid Strategy to work, it would introduce the All-Ireland Covid Action Fund at a cost of €250m to help Northern Ireland also suppress the coronavirus.
People Before Profit would spend over €2.5bn on the health service, which includes bringing private hospitals under public control, increasing staff numbers and bed capacity, while introducing universal free GP care.
The party's plan to protect workers comes in the form of extending the Pandemic Unemployment Payment and Wage Subsidy Schemes for the first four months of 2021, with the strategy expected to protect areas of the economy that would help workers stay in jobs.
It would increase all social welfare payments by €50 and give carers a €1,000 bonus.
On mental health, People Before Profit says it would spend €367m, as it says the pandemic has made it more important than ever to radically increase services in the area.
Spending on housing would be €4.2bn, while investment in public transport capacity would be tripled to include the purchase of 500 new electric buses and public transport would be made free at a cost of €580m.
The cost of all these plans would come in the form of redistributing wealth.
The party said a 10% levy on the profits of pharmaceutical companies and private health companies would net €2bn, a doubling of corporation tax intake would bring in almost €10.5bn, while a 'wealth tax' on the richest 5% of households would add up to almost €4bn.
It would introduce four new rates of tax for high earners from 50-65%, which it says would net €1.3bn.
Elsewhere, Aontú has also launched its alternative budget with a focus on strengthening the health service, by adding beds and increasing staff numbers, and extending the test and trace system for Covid-19.
It would spend €1.5m on a Covid-19 Impact Commission to investigate and understand the impact of the virus on the health service.
The party would invest €40m in Remote Working Hubs to allow people to work in regional towns and villages.
It wants to set up a New Ireland Forum, which it says would work to mitigate against Brexit and to fight Covid-19 on an all-Ireland basis.
The party would investment €2.2bn in the building of 10,000 new social houses and an extra €1.1bn in transport projects, including more bus and rail routes to connect rural areas.
Aontú would introduce a 'vacant site tax' it says would net €6.4m, a plastic tax which would levy €1 per kg of non-recyclable plastic, generating €31m.
Another €120m would be gained from a digital sales and services tax of 3% on those companies the party says has benefited from pandemic.