Labor's election finance reforms are in jeopardy after an eleventh hour breakdown in negotiations with the Coalition on the eve of the last day of the parliamentary year.

Sources close to negotiations told the ABC the opposition had raised last-minute concerns with the government's proposal to limit election donations and spending, which some regarded as a tactic to drag talks beyond the end of the week.

While talks could yet be saved, if the impasse cannot be resolved Labor is instead likely to pursue a deal with the crossbench, where there is strong support for at least one component of the bill – lowering the threshold for donations to be disclosed from $16,900 to $1,000.

Senator Don Farrell has met with colleagues across the parliament in recent days and spoke on Wednesday to two of the most strident critics of the bill, billionaire Clive Palmer and Climate 200 founder Simon Holmes a Court.

Both men would stand to have their political activities curtailed by Labor's full proposal, which would limit any one donor to $600,000 per election, and cap spending at $90 million nationwide for political parties and $800,000 per seat for any candidate.

Crossbenchers have accused the major parties of "stitching up" a deal to preserve their dominance at the expense of small players.

But while the Coalition had hinted at its in-principle support for the plan, it had reserved the right to push for amendments, including increasing the $20,000 limit on how much a donor can give to any one party branch.

The Coalition also has concerns about the $1,000 disclosure rule, which it argues would expose small businesses and individuals to harassment from activists.

While the donation and spending caps would likely not have dramatically affected Labor or the Coalition had they been in place for the 2022 election, previous elections have often seen the Coalition out-raise and out-spend Labor by a large margin, something it could not repeat under the proposed caps.

The electoral reform bill is one of three dozen bills the government plans to put to a vote on Thursday, in what could be the last sitting before the election if Anthony Albanese heads to the polls in February or March.

Several are being negotiated with the Greens and crossbench, including the earnings tax on super funds with balances over $3 million, Reserve Bank reforms, privacy laws, and tax credits for critical minerals.

Others have the support of the Coalition, including migration bills that would dramatically expand the immigration minister's power to force deportations, and the social media ban for under-16s.

But Labor will need to win support for a series of votes to "guillotine" Senate debate and force the bills to a vote, leaving them dependent on the Coalition or the crossbench.