The acrimony between the U.S. Environmental Protection Agency (EPA) and a senior Republican lawmaker has gotten worse. Representative Lamar Smith (R-TX), the chairman of the science committee in the U.S. House of Representatives, today said that the agency has failed to comply with a controversial subpoena to give the panel health data related to air pollution regulations. He said he expects EPA to give him all the material by 30 September.

“You did not provide the Committee with anything new,” Smith wrote in a letter to EPA Administrator Gina McCarthy. Instead, Smith wrote, the agency responded to his 1 August subpoena by providing “a file of already public information along with a letter outlining excuses for why EPA did not comply.”

The data dispute stretches back 2 years and involves data that is, in some cases, decades old. Smith has said he wants raw data from several major studies of air pollution and disease that underpin some of EPA’s air pollution regulations so that independent researchers can review them. The agency and researchers involved in the studies, however, say that the studies have already undergone extensive scrutiny and that releasing the data could violate confidentiality agreements made with thousands of subjects. The issue came to a head on 1 August, when the House science panel approved a subpoena for the data over the opposition of every Democrat.

EPA barely met a 19 August deadline for responding to the survey and didn’t publicly disclose what it had given the committee. It wasn’t enough, in Smith’s view. “[N]either your steps thus far nor the excuses offered … fulfill your obligations under the subpoena,” Smith wrote. His 5-page letter then lays out a number of complaints about how EPA has responded to his request and rebuts some of the agency’s explanations for not providing information.

Smith wants McCarthy to reply by 16 September with a letter “detailing the specific steps” the agency will take to comply.

“I remain hopeful that the subpoena will be complied with in the spirit of cooperation appropriate to relations between Congress and the Executive [Branch],” Smith said in a statement. “If EPA continues to default on its subpoena obligations, I will not hesitate to pursue all other means available to compel production of the relevant data.”