The Turnbull government is facing pressure to ditch company tax cuts in favour of a $75 weekly increase to those living in poverty on unemployment payments.
The Australian Council of Social Service will unveil its budget priorities on Tuesday.
Increasing dole payments by $75 per week would cost $3.2 billion in 2019-2020, the organisation said in its budget priority statement.
Newstart is $538.80 a fortnight for single people.
"It would be a big mistake for this government to press ahead with personal and corporate tax cuts when we're facing major funding shortfalls in vital areas such as the national disability insurance scheme, health, needs-based schools funding, and action to reduce poverty," chief executive Cassandra Goldie said.
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The organisation is calling for a crackdown on the use of private trusts to avoid personal income tax to generate $1.5 billion in revenue in 2019-2020.
Dr Goldie said stamping out the use of private companies to avoid personal income tax could bring in $1.4 billion and curbing international business tax avoidance $500 million.
With an estimated one-in-six Australian children living below the poverty line, Dr Goldie said urgent changes were needed for family welfare payments.
Family payments should be restructured so they no longer decline as children grow older and their costs rise, she said.
She added reforming family payments to better target assistance and reduce child poverty would cost $630 million.
