The Reagan administration said yesterday that it opposes congressional efforts to put new curbs on Wall Street's corporate raiders, contending successful takeovers make industry healthier and the nation richer.

"The available evidence . . . is that unsolicited transactions that affect mergers and acquisitions increase national wealth," Beryl Sprinkel, chairman of the president's Council of Economic Advisers, told the Senate Banking Committee.

"They improve efficiency, transfer scarce resources to higher valued uses and stimulate effective corporate management," he said. "The evidence is overwhelming that successful takeovers substantially increase the wealth of stockholders in target companies."

Sprinkel testified in opposition to a bill proposed by Sen. William Proxmire (D-Wis.), the banking committee's chairman, that has been tagged as a solution to takeover abuses.

The Securities and Exchange Commission also faulted the Proxmire bill, saying it would "alter fundamentally not only the market for corporate control, but also the structure and operation of the nation's securities markets as a whole."

The bill's introduction follows Wall Street's insider trading scandal, which centers on brokerage merger and acquisition departments and on arbitrageurs, speculators in the stock of takeover targets.

But it raises many issues of its own, such as greenmail, golden parachutes and poison pills, which are used as defensive tactics by managers.

Sprinkel said the debate "is notorious for its hyperbole," with terms conveying "pejorative, militarist images." But he called that portion of the debate "unsupported rhetoric and irrelevant arguments," and contended that the real evidence of business does not support the calls for stronger rules on takeovers.

Managers who must face the possibility of being taken over should they not perform "must continually explore new ways to make America's corporations more productive and more competitive in the world economy -- and this result clearly benefits American consumers and workers as well as the shareholders themselves," Sprinkel said.

Sprinkel was backed by Charles C. Cox, acting chairman of the SEC, who said the bill "would effect a radical departure from the historical role of federal securities regulation.

"The enactment of restrictions on open market purchases and partial ownership of corporations . . . would impair the depth and liquidity of the markets and the formation of capital," Cox said.

Current law provides that a corporate raider must publicly disclose stock purchases within 10 days of acquiring a 5 percent ownership interest. That has been criticized as allowing a 10-day "window" for quickly buying up stock, possibly in collusion with other purchasers, before the public learns of the takeover attempt and prices soar.

Proxmire would close that window by requiring a filing by the close of trading on the next business day after passing a 3 percent mark.