The D.C. Board of Elections and Ethics formally refused for the second time yesterday to accept citizen petitions for a public vote on the city's proposed convention center, apparently forcing the issue into court.

Spokesmen for the Convention Center Referendum Committee, which has collected 12,000 signatures in seeking a vote on the issue, asked the board either to accept the petitions or to take a firm stand in refusing them.

By a vote of 2 to 0, with one member abstaining, the board chose the latter course, setting the stage for a legal test.

The committee, a citizen group headed by economist John J. Phelan, is seeking to use a referendum procedure approval by city voters at the election in Novermber 1977, and later affirmed by Congress.

That procedures would permit Washingtonians to vote on whether they want to spend nearly $100 million to build the facility on Mount Vernon Square, north of downtown.

However, the D.C. City Council failed to adopt legislation setting up rules and procedures for a referendum on that or any other civic issue. That posed a legal question on whether the board of elections could conduct an election without council action on such rules.

In October, the elections board voted 2 to 1 to adopt a policy that the board has no legal authority to accept the petitions without the legislation. Yesterday's vote affirmed that position, although retiring board chairman Shari B. Kharasch, who voted with the majority, said she did so only to provide a way for the referendum committee to take the issue into court.

The citizen group hopes to get the issue on the ballot May 1, when city voters will elect a successor on the council to Mayor-elect Marion Barry and City Council Chairman-elect Arlington Dixon (D-Ward 4).

In a related development, the D.C. Corporation Counsel's Office has notified Chief Judge H. Carl Moultrie of the D.C. Superior Court that it plans to file condemnation suits in February to acquire land for the convention center. By law, the city would have to deposit funds equal to the estimated value of the property with the court when it files the suits.

Also, the corporation counsel's office has approved the payment of $586,678 in congressionally appropriate funds to several city banks that advanced money to the city to plan the Eisenhower Center, the forerunner of the proposed convention center.