A tax called the community infrastructure levy, which would require any organisation that gets permission to develop land to pay a tax based on its value, is due to be introduced by the Planning Bill.
It would affect organisations that are building business premises or new offices, as well as extensions to existing buildings.
A group of peers, including crossbencher Lord Cameron of Dillington, is seeking to amend the bill so that the tax does not apply to charities.
Cameron told Third Sector that he would introduce an amendment to exclude charities from the bill, which will be debated at committee stage this month.
"Charities are contributing to the infrastructure, not being a drain on it, and it's completely unfair they should have to pay this tax," he said. "It's most important that we get the amendment on the face of the bill and don't accept any promises from government.
"I hope that by the time we get to this section of the bill, I will either have an amendment that's satisfactory to government or have agreed a joint amendment with other peers."
Helen Donoghue, chief executive of the Charities Tax Group, which has formed a coalition of charities to campaign against the measure (3 September, page 1), said: "If the levy hits the sector, the effects would be catastrophic. A lot of charities won't be able to operate at all, and a lot of things won't get built."