In what are believed to be his first public remarks on the subject, US Energy Secretary Steven Chu came out against California’s Proposition 23 today. Chu said passage of the measure, designed to suspend the state’s landmark climate law known as AB 32, would be “a terrible setback.”

Asked by KQED News reporter Gabriela Quiros what Chu thought of the measure to sideline AB 32, slated for November’s ballot, Chu said:

“That would be a setback. AB32 was a good bill and continues to have California in a leadership role in developing clean energy and the efficient use of energy. From the middle 1970s, California played that role and it would just be a terrible setback.”

Chu made the comment while meeting with reporters after today’s dedication of Stanford’s $420 million Linac Coherent Light Source (LCLS) in Menlo Park. Billed as the world’s most powerful x-ray laser, scientists say it could one day create, among other things, energy sources that emulate photosynthesis.

Chu, who directed Lawrence Berkeley National Laboratory before being tapped by the Obama administration, has been a vocal proponent of climate action and development of renewable energy.

The energy secretary is only the latest in a parade of high-profile government and technology leaders to openly oppose Prop 23. Last week, Mary Nichols, who directs implementation of AB 32 as chair of the California Air Resources Board, called Prop 23 “a very serious threat” to the state. Both major gubernatorial candidates appear to oppose it. Democrat Jerry Brown has deplored it and Republican Meg Whitman has said she will “in all likelihood” vote against it. The measure is supported by the Howard Jarvis Taxpayers’ Association, the National Federation of Independent Business, and various companies in the oil and gas industry.