Brokers and insurance agents providing retirement-savings advice would have to put clients’ interests ahead of their own under an Obama administration plan that will face stiff opposition from Wall Street and Republican lawmakers.

The Labor Department proposal announced Tuesday is a win for Democrats and consumer advocates, and a setback for bankers who had angled for a standard to be set by the Securities and Exchange Commission, which oversees a broader range of investment activities. Adoption of a final rule could take six months or longer, according to RBC Capital Markets, providing plenty of time for congressional scrutiny and industry lobbying.

Under the plan, brokers would have a legal duty to put clients’ interests first, a shift that could reshape how they steer clients and collect fees, and potentially create winners and losers among mutual funds and other products. The changes would extend protections to the $7.4 trillion held in IRA accounts, a common vehicle for retirement savings that barely existed when the original rules were issued 40 years ago.

“This rule is intended to provide guardrails, but not straitjackets, so we know consumers are getting advice that is in their best interest,” Labor Secretary Thomas Perez told reporters on a conference call.

President Barack Obama endorsed Labor’s plan in February, putting new momentum behind the effort to revise rules that affect tens of millions of baby boomers nearing retirement age and workers who don’t have pension plans. It’s also backed by Senator Elizabeth Warren, the Massachusetts Democrat who has scolded banks over their treatment of consumers.

Lobbying Effort

Wall Street has spent more than four years lobbying against Labor’s effort. Led by banks such as Morgan Stanley and Wells Fargo Advisors, the industry has argued that costlier regulations could take away options for smaller investors.

Brokers won concessions, including a framework that would let them continue selling bonds out of their own inventory. Morgan Stanley questioned whether an earlier version of the plan, issued in 2010, would have barred such transactions.

Trade groups such as the Securities Industry and Financial Markets Association are expected to focus during the 75-day public comment period on the rule’s 250-page economic analysis, which outlines its costs and benefits.

“This is a voluminous rule where the fine print matters,” said Kenneth Bentsen, Sifma’s chief executive officer. “We want to ensure it protects investor choice and doesn’t unnecessarily reduce access to education or raise costs, particularly for low- and middle-income savers.”