WASHINGTON — The boasts of Congressional Republicans about their cost-cutting victories are ringing hollow to some well-known economists, financial analysts and corporate leaders, including some Republicans, who are expressing increasing alarm over Washington’s new austerity and antitax orthodoxy.

Their critiques have grown sharper since last week, when President Obama signed his deficit reduction deal with Republicans and, a few days later, when Standard & Poor’s downgraded the credit rating of the United States.

But even before that, macroeconomists and private sector forecasters were warning that the direction in which the new House Republican majority had pushed the White House and Congress this year — for immediate spending cuts, no further stimulus measures and no tax increases, ever — was wrong for addressing the nation’s two main ills, a weak economy now and projections of unsustainably high federal debt in coming years.

Instead, these critics say, Washington should be focusing on stimulating the economy in the near term to induce people to spend money and create jobs, while settling on a long-term plan for spending cuts and tax increases to take effect only after the economy recovers.