The city comptroller is being asked to decide whether the city should stop providing lawyers to defend the Republican National Committee in court.

For more than a year, the city law department has been representing the Republican National Committee in a lawsuit brought by a protester arrested at the 2004 Republican National Convention in New York City. According to the suit, the city and the Republican National Committee conspired to stifle protests. The city has denied the allegation.

In a letter sent Monday, a lawyer who represents the protester, Karen Wohlforth, sent a letter to the city comptroller, William Thompson, and the state attorney general, Andrew Cuomo, to investigate the legal arrangement between the city and the Republican National Committee.

“In view of the fact that public monies are being expended in order to defend the Republican National Committee in this matter, we respectfully request that you investigate the propriety of this representation,” Ms. Wohlforth wrote.

The indemnification agreement signed by the city before the 2004 convention requires it to pay legal fees for the national committee in most instances. The contract is not unusual, lawyers say.

“This kind of an agreement is a very common provision when large-scale events like this are involved,” a lawyer for the city, Jeffrey Dougherty, said in an e-mail message. If the city “were not to offer such a provision, it could not conceivably compete to host such an event,” he said.

Mr. Dougherty represents both the city and the Republican National Committee in the suit. That arrangement was first reported last year in the New York Law Journal.

Initially, a private attorney from Albany represented the Republican National Committee in the case. But in December 2005, the chief counsel for the committee, Thomas Josefiak, told the court that the city would supply an attorney for the committee, according to court records.

Mr. Josefiak could not be reached yesterday for comment.

In legal papers filed last year, Ms. Wohlforth said the arrangement could pose a conflict of interest for the city. She suggested that the city may have offered to represent the Republican National Committee to control the legal strategy in the case, one of dozens of lawsuits the city faces over the arrests of hundreds of protesters at the convention.

“The RNC is not leaning on the contract,” Ms. Wohlforth told The New York Sun. “It is the city that is leaning on it.”