WASHINGTON — The consumer protection agency that was created in the wake of the financial crisis launches today lacking key powers that Congress had intended to give it.

The Consumer Financial Protection Bureau will begin this week to enforce dozens of rules that Congress lumped together as part of last year’s overhaul of financial regulations. It will help ensure that credit-card holders have a clear understanding of the plastic in their wallets, borrowers are protected from unfair lending and military families have a dedicated financial watchdog.

Yet without a confirmed director, the agency can’t write or enforce new rules for nonbank financial companies, which made about half of the riskiest subprime loans before the crisis. The agency was created as the first federal regulator for many of these companies. Lawmakers wanted to prevent them from sidestepping rules that already applied to banks.

For payday lenders, prepaid card companies and other nonbanks, the new rules may be a little like the 1930s and the advent of the Securities and Exchange Commission, says Eugene Ludwig, who was comptroller of the currency, the top regulator for national banks, during the Clinton administration.

The lack of a confirmed director means those companies have less to worry about in the short term. President Obama’s choice for the job is former Ohio Attorney General Richard Cordray.

Republicans say they will block him or any other nominee until the power of the agency and its director are scaled back. They have introduced legislation that would replace the agency’s director with a five-person commission and give Congress more control over its budget. The Democratic-controlled Senate is unlikely to take up the measures, and Obama said Wednesday that he would veto them.

Supporters of the agency say it will be more effective than its predecessors because it has a single focus: making sure consumers are treated fairly by banks, lenders and other financial companies. They say Americans and the companies will be stronger financially as a result.

Before the financial overhaul, the responsibility for protecting consumers was shared among seven agencies that also were responsible for making sure banks stayed healthy. That sometimes presented conflicts, such as when banks increased their use of steep overdraft fees. Because the regulators were focused on banks’ financial performance, consumers often lost out.

Banks are nervous that the agency’s rules will make it difficult to profit from some products. That would discourage them from developing new offerings that consumers might want, they say.

Until Congress confirms Cordray or another director, Treasury Secretary Timothy Geithner will serve as the agency’s acting director. Elizabeth Warren, the Harvard Law School professor tapped by Obama to help set up the agency, will return to teaching.