Sen. Alfonse M. D'Amato (R-N.Y.) yesterday temporarily postponed his plan to introduce a controversial union-backed bill that would prohibit "double-breasting," the practice by which unionized construction companies create nonunion subsidiaries, according to Senate sources.

D'Amato postponed action after a handful of Republican senators wavered on earlier indications that they would support the measure, according to GOP and Democratic staff members.

"D'Amato probably believed he didn't quite have the votes, and the Senate leadership didn't want a filibuster," said Charles Hawkins, a lobbyist for the Associated Builders & Contractors, one of scores of business groups and corporations opposing the bill, which the AFL-CIO supports. D'Amato was unavailable for comment.

The AFL-CIO's 15 building-trades unions, many of which have strong ties to the Republican Party, have pushed hard for the bill, asserting that construction firms have unscrupulously evaded union contracts by creating nonunion offshoots that perform work previously done by unionized workers. The bill easily passed the House last April.

D'Amato, who has received substantial union support in his reelection campaign, has also gotten considerable backing from business groups which oppose the bill. He had planned to attach the House-approved bill to the pending resolution to raise the federal debt ceiling, but now intends to seek another route, probably in September, sources said.

Corporate lobbyists, caught by surprise when the bill passed the House 229 to 173, have campaigned intensely against the measure, saying it could force nonunion companies and their employes to become unionized against their will.

The bill, an amendment to the National Labor Relations Act, said that any two construction firms having "direct or indirect common ownership, management, or control" would be considered a single firm for the purposes of labor law.