Mayor Bloomberg spent more campaign funds in 2011 than any candidate in New York — and he’s not even running for office.

Bloomberg dished out $5.64 million of his personal fortune this year to prop up his public image — dwarfing the second- biggest spender, Steve Bellone, the Democratic candidate for Suffolk County executive, who has shelled out $2 million so far, the analysis by the New York Public Interest Research Group found.

Erie County Executive Chris Collins, a Republican who is running for re-election, came in a distant third, spending $1.1 million from Jan. 12 through Oct. 24.

Still, the amount spent by Bloomberg is a pittance compared to the more than $100 million he spent on his successful re-election to a third term in 2009. He won’t face the voters again — at least for the mayoralty.

“In politics, it’s always nice to have deep pockets,” said Rob Ryan, spokesman for Angie Carpenter, the GOP candidate running for Suffolk County executive.

The Bloomberg camp emphasized that the mayor opened his wallet this year to counter TV and radio attack ads from the United Federation of Teachers and other unions. The UFT waged a successful campaign to block Bloomberg’s bid to get Albany to scrap the “Last In, First Out’’ law that determines teacher layoffs.

In March and April, Bloomberg spent $2.8 million on TV ads, $2.48 million in direct mail and $355,000 on polling.

The Bloomberg ad splurge came after the public beating he took during the city’s botched response to last December’s snow storm.

In March, the Quinnipiac University poll found that only 39 percent of the city residents approved of Bloomberg’s job performance, his lowest rating since 2003.

But a month later, only 40 percent approved of the job he was doing, despite the massive media campaign. Last month, 47 percent gave Hizzoner a thumbs-up after he was lauded for his handling of Hurricane Irene.

“It just shows that money is not an issue for Bloomberg at all. This is also one of the reasons he has been successful over the past decade,’’ said NYPIRG’s Bill Mahoney, who conducted the analysis.

Hunter College poli-sci Professor Ken Sherrill said billionaire Bloomberg is using his financial resources to strengthen his political authority while he’s a lame duck.

“It’s a matter of maximizing his power. He has to negotiate a budget with the City Council and has to deal with a popular governor,” Sherrill said.

“The more popular he is, the better off he is. People are more likely to say ‘no’ to the mayor if he is unpopular. If Bloomberg is popular, he’s a force to be reckoned with.”