The regulators are trying to prevent the kinds of practices that dumped so many risky mortgages into the financial system several years ago.
But the proposal has sparked concerns from some groups, which worry that a 20 percent down payment is too onerous for many working-class borrowers. Banks also oppose the heightened down-payment requirement, which regulators had considered setting as low as 10 percent.
The proposal, which could be made official this summer, is unlikely to make a major difference in the market for a while, because most home loans are insured by federal agencies using taxpayer dollars. Those mortgages would be exempt from the proposed requirements.
The regulatory effort comes as the Obama administration and House Republicans have made proposals to begin winding down Fannie Mae and Freddie Mac, the government-backed mortgage giants, in part by reducing the competitive advantages they have over banks. This could include requiring that the two mortgage firms begin charging higher fees. The aim would be to draw private firms back into the mortgage market, which they exited during the financial crisis.
In the years leading up to the financial crisis, lenders could hand off loans — many of them high risk — to other companies for a fee. Without skin in the game, they could continue to make risky loans.
Officials say the new rules would correct that.
“Properly aligned economic incentives are the best check against lax underwriting,” said Sheila C. Bair, chairman of the Federal Deposit Insurance Corp., which announced the beginning of the public comment period on the proposed rules.
The new standard was proposed by the FDIC and the Federal Reserve. Other regulators are expected to follow suit.
The rule, known as “risk retention,” would require that mortgage lenders invest in the loans they make, so if the loans go bad, the lender would suffer. Lenders would have to accept 5 percent of the losses.
But banks would not have to retain any risk for mortgages made to borrowers who put down at least 20 percent — making the loans relatively safer. As a result, the cost to the banks would be less, and they would be able to offer lower interest rates for these loans.
Some critics say these conditions would keep eligible borrowers from getting good terms on their loans.
“If we require 20 percent down payments to get a loan, we will ensure broad swaths of working- and middle-class people will not be able to get a loan,” said John Taylor, chief executive of the National Community Reinvestment Coalition, a group advocating an extension of credit to low- and moderate-income borrowers.