Mayor Bloomberg says there’s nothing the city can do about soaring gas prices, but a Democrat who wants to be mayor isn’t so sure.

The city comptroller, William Thompson Jr., is responsible for seeing that the city’s pension funds earn high rates of return. But that’s not stopping him from taking on big oil companies whose high stock prices make those funds bulge.

Mr. Thompson fired off a letter yesterday to ExxonMobil, asking the oil giant to investigate allegations of price gouging and complaints about unjustly high executive salaries. City pension funds own $1.2 billion worth of ExxonMobil stock, and more in other oil companies. Mr. Thompson is trying to use the funds’ financial muscle to pressure all of them.

“Are short-term earnings good for the portfolio? Sure,” Mr. Thompson told The New York Sun during a phone interview. “But in the long run there is greater damage being done to the companies.”

Oil companies are making record profits and are among the pension funds’ best-performing stocks. As a result, some say Mr. Thompson’s action could hurt pension holders.

He denied that his actions were driven by politics, saying he has long used the fiscal leverage of the pension funds to influence company practices. “I don’t think it has anything to do with 2009, and I think it has everything to do with the job I’m in now,” Mr. Thompson said. “In that regard, it’s incredibly consistent with what we have done for the last four or four and a half years and what city comptrollers have done in the past.”

In the letter to ExxonMobil, Mr. Thompson wrote: “I am concerned that the growing perception of unfair windfall profits and egregious executive pay could strengthen the maelstrom of public outrage, pose significant long-term risks to the company’s reputation, and negatively affect consumer preference at gas stations around the country.”

Through a spokesman, the state comptroller, Alan Hevesi, declined to say whether he will take action on behalf of the state’s retirement fund. In the past, both comptrollers have worked together on these kinds of issues.

Aides to Mr. Hevesi said the public retirement fund owns about $2.8 billion worth of stock in six American-based oil companies. The stock value has increased by about $92.5 million since the end of February.

Attempting to tame the recent spikes in gas prices has become politically popular for lawmakers. But the vice president of the Business Council of New York State, Edward Reinfurt, said any letter to ExxonMobil from the city’s pension funds – which are being invested on behalf of working and retired teachers, firefighters, police officers, and civil servants – should start with a “thank you for your fiscal performance.”

“I think Exxon’s track record has been nothing but impressive,” Mr. Reinfurt said.

He said that while shareholders have the right to express concerns, the primary responsibility of the city’s pension fund is to get a good return on investment.

The letter that Mr. Thompson sent, which went to the company’s audit and compensation committees, also said he had concerns that ExxonMobil has no plans to invest in alternative and renewable energy.

A spokesman for ExxonMobil, Russ Roberts, said the Federal Trade Commission has investigated price gouging more than 100 times and has never uncovered illegal practices.

He also said ExxonMobil does research fuel alternatives and that it is the largest purchaser and blender of ethanol in the industry.

“The success of our company is directly related to the success of the pension fund holdings,” Mr. Roberts said.

Earlier this week, the CEO of the oil giant, Rex Tillerson, told Matt Lauer on the “Today” show: “A lot of pension plans, a lot of teacher retirement plans” are among our shareholders, “and our job is to go out and make the most money for those people so their pensions are secure so that they see the benefits of our work.”

The president of the United Federation of Teachers, Randi Weingarten, criticized that rationale and praised Mr. Thompson.

“It’s outrageous that ExxonMobil would try to hide behind pension funds in defending their price gouging,” Ms. Weingarten, who is also head of the city’s Municipal Labor Council, said.

“The pension funds have to be invested in fiscally sound ways, but there is also a social responsibly here,” she said.

Meanwhile, Mr. Bloomberg has suggested that it’s not the place of the government to penalize oil companies for making money.