An LIRR strike would cost the economy of Long Island and New York City up to $50 million per day, the state's top fiscal officer said Tuesday.

State Comptroller Thomas DiNapoli estimated that economic activity, from tourism and small businesses to Broadway shows and restaurants, would be hit hard by a work stoppage at the Long Island Rail Road.

A strike could be "devastating," he said, for delis, newsstands, dry cleaners and other shops that serve commuters, and for communities, such as Long Beach and Montauk, that rely on visitors coming by train.

"There will be no winners who come out of this, only negatives at a time where we can least afford it," DiNapoli said, referring to Long Island's slow recovery from superstorm Sandy in 2012 and the housing collapse and Great Recession, which both began in 2007.

"Many of the Mom and Pop shops around the stations ... some of them are just about making it," he said in an interview. "You could see some of these folks perhaps having to close their doors."

DiNapoli, a Democrat from Great Neck Plaza, also said a walkout by the LIRR's unionized workers would coincide with the height of the tourism season, a key component of the $5.6 billion leisure and entertainment industry in Nassau and Suffolk counties. Consumer spending lost now won't be made up, he said.

DiNapoli called his up-to-$50-million-per-day estimate of a strike's economic impact "conservative ... it could be higher than that." The figure is based on LIRR ridership, census data and other statistics.

For comparison, the size of the Island's economy was about $137 billion last year, based on the value of all goods and services produced here, according to the forecasting firm IHS Global Insight.

The Regional Plan Association, a Manhattan-based think tank, estimated earlier this year that 30 percent of Nassau residents and 11 percent of Suffolk residents commute to New York City, and one-third of them take the LIRR.

And $1 out of every $4 of income earned by local residents comes from employment in the city.

The Long Island Commuter Council, which represents riders, endorsed DiNapoli's impact estimate yesterday. Council executive director William Henderson said: "A strike would be a major blow to Long Island and the entire region."

The Metropolitan Transportation Authority, through a spokeswoman, said, "We hope the unions heed this message that they ought to modify their unreasonable demands instead of continuing to threaten a nightmare for everyone on Long Island."

A spokesman for Gov. Andrew M. Cuomo said he would have no comment, while an official for the LIRR unions didn't respond to a request for comment.