Shadow chancellor John McDonnell is accusing Boris Johnson of allowing the country's "super rich" to buy access to "tax breaks and corporate giveaways".
Labour published research which, it said, showed 48 of the 151 billionaires listed in the latest Sunday Times Rich List had donated more than £50 million to the Tories since 2005.
The opposition party has calculated that by 2023/24, the Conservatives will have handed out "tax breaks and corporate giveaways" worth almost £100 billion since coming to power in 2010.
Labour said they included £86 billion in corporation tax cuts, £5.6 billion in reductions to inheritance tax and £5.5 billion in cuts to capital gains tax.
In a speech on Tuesday, Mr McDonnell will accuse the Tories of siding with "the billionaires, the bankers and big business".
Speaking in London, he will say: "No one needs or deserves to have that much money, it is obscene.
"It is also obscene that these billionaires are buying access and tax breaks to Boris Johnson's Conservative Party.
"We know whose side Boris Johnson is on – the billionaires, the bankers and big business.
"Jeremy Corbyn and the Labour Party are on the side of the people, offering real change for our country, putting wealth and power in the hands of the many, not the few."
The Conservatives said the "top 1%" were paying a greater share of taxes than at any time under the last Labour government while tax receipts from business were at an all-time high.
Treasury Minister Simon Clarke said: "Corbyn's Labour have revealed their true colours. They want to stop people from passing on their family homes to their children after they die.
"Rather than helping people to succeed, they want to take away your family home in higher taxes. Their plans would not hit billionaires – they would overwhelmingly hurt hard-pressed families."