George Osborne's plans to slash taxpayer funding for the opposition could be watered down to protect smaller parties in the Commons.
The Chancellor announced proposals in November to cut so-called Short money allocations to opposition parties by 19% and then freeze them in cash terms until 2020.
Now a consultation document has suggested there could be "tiered" reductions, so not all elements of the grant are affected in the same way, with a funding floor built in to protect smaller parties.
The consultation asks whether the 19% cut is the right benchmark and whether increases in line with inflation should be restored after 2020.
The document also suggested changes to the formula to give more weight to the number of MPs rather than the amount of votes a party received, because Short money is meant to support parliamentary work.
The move could come as a blow to parties such as Ukip, which received 3.9 million votes but won just one seat, or the Green Party, which had more than a million votes but just one MP.
The document asks: "Should greater weighting be given in the formula to the number of MPs that an opposition political party has, and less to the weighting for votes cast?"
The consultation also seeks views on whether there should be greater transparency in the way the funding - some £9.5 million in 2015-16 - is spent.
"Given the Government's broader transparency agenda, which includes local and central government being asked to publish details of their spending, there is a case for greater openness on how Short money is spent," the document said, suggesting that parties could provide information to be published on Parliament's website, potentially in the form of audited accounts.
Under the current system, to qualify for funding parties must have at least two MPs, or one MP and more than 150,000 votes. Parties meeting the threshold then receive £16,956 for every seat won at the most recent general election plus £33.86 for every 200 votes gained.
A travel fund worth £186,269 in 2015-16 is also split in line with the formula, and Jeremy Corbyn's office as Leader of the Opposition is entitled to about £789,979.