The Government is considering an amendment to the Charities Bill to oblige charities to publish group accounts.
The amendment, tabled by former Refugee Council director Lord Dubs, would require charities to show the financial results of the parent charity and any trading subsidiary as one.
Government spokesman Lord Bassam said ministers would give the amendment "further thought". But he added: "We must have regard to important issues of proportionality and the practicality of introducing such a provision at this late stage in the legislation."
Dubs described the amendment as "a fairly moderate suggestion. Some charities do this automatically, although currently they are under no obligation to do so. I think it might be better if they were."
But the amendment was opposed by Lord Phillips of Sudbury. He claimed that it would not be clear from consolidated accounts which assets were charitable and which belonged to the trading subsidiary.
Sophie Chapman, policy and campaigns officer with the Charity Finance Directors' Group, said: "We were heartened by the Government's positive response. We believe this is a lone opportunity to clear up a legislative anomaly and is therefore well worth the practical effort.
"Although it was rightly pointed out that most large charities already conform to this practice, it is still theoretically possible for huge amounts of income from trading subsidiaries to be disguised in some charities' accounts."