The Virginia House of Delegates tonight defeated an effort to put the proposed federal Equal Rights Amendment to a statewide vote.

By a vote of 50 to 36, the House returned a bill requiring a 1980 referendum on ERA to the Privileges and Elections Committee. The maneuver effectively kills the measure for this session.

The referendum was proposed in a bill sponsored by Del. Robert L. Thoburn (R-Fairfax), an ardent opponent of the ERA.

Thoburn's bill was approved yesterday by the P&E Committee, 15 to 2, Tonight, however, Del. Dorothy S. McDiarmid (D-Fairfax), chief patron of resolutions in the House calling for ratification of the ERA, strongly urged the delegates to kill the referendum.

"There has been a long, long effort to sweep ERA under the carpet," McDiarmid said. "This is another one. A referendum in 1980 would preclude consideration of ERA next year. After this year's election, we may have some new people here who think ERA is a fine thing."

The House of Delegates has never debated ERA on the floor because a ratification resolution has never been reported by the P&E Committee. The committee rejected the proposed amendment again this year, 12 to 8.

In other action, the House gave preliminary approval to a bill that would permit businesses to install pay telephones and charge any amount up to 20 cents a call for their use. Del. Erwin S. Solomon (D-Bath) said that his measure is an effort to introduce competition in pay telephone rates.

The House also gave preliminary approval to a bill transferring 1,200 feet of Atlantic Ocean beachfront from the Virginia Army National Guard to the division of state parks. The beach at Camp Pendleton in Virginia Beach would become the first accessible Atlantic Ocean-front park in the state.

In the Senate, legislators approved the following:

A bill sponsored by Sen, Charles Waddell (D-Loudoun) that would require drive-in theaters that show X-rated movies to construct a road barrier to hide the screen from passing motorists.

A resolution sought by residents of King George and Stafford counties to request that the District of Columbia stop transporting sewage waste to treatment facilities in their areas.

But a Senate committee killed another measure designed to allow teacher groups to "meet and confer" with school boards on their working terms and conditions. Lawmakers who opposed the bill argued it would allow collective bargaining by public school teachers, who number about 60,000 in the state.