International Development Secretary Priti Patel is facing accusations of planning to channel billions of pounds into the private sector arm of the UK's aid programme.
In a draft bill seen by the Financial Times newspaper, the Department for International Development (DfID) is proposing to increase the limit on support it can give to the CDC Group, formerly the Commonwealth Development Corporation, from £1.5bn to £6bn ($1.9bn to $7.5bn).
The bill also includes provisions for Patel to double that limit to £12bn with parliamentary approval.
The CDC has been criticised in the past for pouring taxpayer-funded aid money into luxury housing, gated communities and other private ventures in the global south.
"The International Development Secretary, Priti Patel, has a serious case to answer in continuing with the privatisation of aid through the CDC Group," said Saranel Benjamin, international programmes director at the anti-poverty charity, War on Want.
"Increasing government support to this overseas private equity firm is a slap in the face for taxpayers whose hard earned tax money is going to fund private business ventures in the global south."
Labour MP Stephen Doughty criticised the bill as an "attempt by stealth" to increase the amount of taxpayer money that can be funnelled into the CDC.
"With the government admitting already to parliament that over 25 per cent of our aid budget will be spent in future via other government departments, this could see over half our aid diverted or contacted out from the very department supposed to oversee it," he was quoted as saying by the Independent.
But a spokesman for the DfID said the increase in the CDC finance ceiling did not "commit us to increases in financial support".
"We will only invest in CDC when it is needed to meet demand, achieve value for money and continue delivering life-changing results and clear development impact," he was reported as saying.