Angela Rayner suggested Rachel Reeves should hike taxes on wealthier people and banks, according to a leaked memo.
The Deputy Prime Minister's department reportedly wrote to the Chancellor in March with the "alternative" suggestions ahead of her Spring Statement.
According to the Telegraph, it was suggested the Treasury should increase tax rates paid on dividends and reinstatethe lifetime allowance.
The allowance limited how much savers could put in their pension pot before incurring a higher tax charge and was abolished under the Tories. They also floated closing the commercial property stamp duty loophole and a higher corporation tax rate for banks.
The memo titled "alternative proposals for raising revenue" estimated eight changes could raise £3billion to £4billion a year. The proposals were not adopted by the Chancellor.
It comes as the government faces intense anger among MPs over £5billion in cuts to sickness and disability benefits announced at the time.
Liz Kendall, the Work and Pensions Secretary, is expected to defend the controversial reforms in a speech today despite a looming rebellion.
Over 100 Labour MPs have written to the Chief Whip suggesting they cannot support the government - leading to fears faces his biggest Commons revolt yet.
Some left-wing MPs in the party have also urged the PM to introduce a wealth tax on the assets of the country's super-rich to avoid disability benefit cuts.
Environment Secretary Steve Reed told the on Wednesday: "You wouldn't expect me to comment on leaks and speculation. But I know from being in the Cabinet when discussions happen, the Cabinet is united behind the government's Plan for Change.
"In fact the government has increased taxes on the wealthy. We have brought non-doms - those are those foreign billions who live in our country, who were paying no tax previously, now they are liable to paying their taxes like everyone else."
A government source also said it is normal practice for Cabinet colleagues to have such discussions. They should not be read as an endorsement of any particular idea or proposal, they added.
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