A new report has provided evidence to back up what brokers have been saying: it is harder for stores to find retail space in the prominent shopping corridors, with rents jumping as much as 75 percent on Fifth Avenue from 42nd to 49th streets since just one year ago.

Ground floor asking rents have reached an average of $900 per square foot — up 75 percent from last spring — on the key Midtown stretch of Fifth Avenue, according to the Real Estate Board of New York’s Spring 2012 Retail Report.

The advisory group attributed this growth in asking rents both to the lack of space on Upper Fifth Avenue, causing a trickle-down effect, and the high degree of pedestrian traffic everywhere along the avenue including crosstown walkers from Grand Central Terminal.

Average asking rents on Upper Fifth Avenue between 50th and 59th Streets have edged up 22 percent to $2,750 per square foot for ground spaces since last spring.

In other locations:

* Despite increases in all the prime East Side corridors, average asking rents for all space on the East Side declined 13 percent since a year ago. This is partly due to a falling off of aggressive bank leasing and the ongoing Second Ave. subway construction.

* Rents are down 13 percent in Times Square but they still average $1,400 a square foot and there are only two availabilities.

* West Village rents are down 7 percent although asking rents are still averaging $452 a square foot.

* SoHo and Herald Square are once again getting squeezed with rents up 11 percent and 23 percent, respectively.

* Average asking rents for ground floor space on Madison Avenue between 57th and 72nd streets increased 31 percent to $1,203 a square foot.