Bicycle riders pose a growing danger on city roads, said a Bronx politician seeking to put registration plates on bikes and slap fines and jail time on offending pedalers.

The bill, introduced by City Councilwoman Madeline Provenzano, calls for fines up to $300 and up to 15 days in jail for anyone over 16 years old who rides an unregistered bike or flouts traffic laws.

Transportation Alternatives, a bicycle advocacy group, said yesterday that its members have sent more than 1,500 faxes to Provenzano's office saying the bill is misguided. They say it would discourage bike riding among the city's 112,000 daily riders, promoting traffic and pollution.

"It's clear that she does not like bike-riding, which is why her introduction of this bill is a blatant attack against bike-riding," said Noah Budnick, projects director at Transportation Alternatives.

Provenzano, a Democrat, said she received complaints about bicyclists. "They zigzag in and out of traffic, they're on the sidewalk, they're a danger to senior citizens," she said.

Provenzano foresees a registration fee of about $25 or less with the city Department of Transportation or another agency that would be in charge of registering the bikes and issuing mini plates. Bikes also could be impounded under the plan.

Criticism that she doesn't understand that cycling is a growing and popular activity among New Yorkers is wrong, Provenzano said. She said her family are bike riders, although she never rides.

"That's one of the reasons I think it's a good piece of legislation because riding a bike has gotten to be so popular," she said.

The bill would have to pass through the council's transportation committee chaired by Councilman John Liu (D-Flushing) before it goes for a full council vote.

Asked about the bill's chances yesterday, Liu offered a less-than diplomatic response.

"When I was a kid, I had a license plate on my bike," Liu said. "I'm trying to remember which cereal box I got it from."

A spokesman for the Transportation Department did not return a call for comment. But the city Parks and Recreation Department, which may be called on to issue summonses in parks, was supportive.

"Anything that encourages safer riding and observations of traffic regulations is a good idea. Warner Johnston, a Parks spokesman, said. "It will improve safety for pedestrians and other park users."