ESCONDIDO -- Take a guess: How many illegal immigrants are there in Escondido? The size of the population of illegal immigrants has perplexed demographers because there are no accurate counts -- in Escondido, the state or the country.

But Escondido Councilman Sam Abed says he has the answer.

Abed, a gas station owner, says one in four of the city's residents is an illegal immigrant. That many illegal immigrants are overcrowding apartments, straining city resources and deteriorating the quality of life for other city dwellers, he said. That's why he supported the city's new rental law, which prohibits landlords from renting to illegal immigrants.

Opponents of the rental ban say it is unconstitutional and will lead to discrimination against Latinos. Several civil and Latino rights groups filed a lawsuit against the city Friday to keep it from implementing the law.

In a recent nationally televised interview, Abed repeated his unsubstantiated figure.

"We have about 35,000 illegal immigrants, an estimate, out of 140,000 residents in our city," Abed told Fox News last month. "That's a huge number. The impact on our culture, on our sovereignty, on our education system and our health care has been tremendous."

Several researchers say Abed's figures may be inaccurate.

"His numbers are questionable," said Rob Paral, who recently completed a study on the illegal immigrant population by congressional district.

Abed has said he arrived at his 35,000 figure by extrapolating data from a study, based on the 2000 U.S. Census, that found about half of the Latinos in Vista were ineligible to vote because they are not U.S. citizens. Abed said he calculated that, because Escondido and Vista have similar demographics, half of Escondido's Latinos were illegal immigrants.

But that's too far of a leap, said Jeffrey Passel, a senior research associate with the Pew Hispanic Center who has studied the size of the illegal immigrant population.

"To go from ineligible to vote to illegal immigrant is simply wrong," Passel said.

Abed, a naturalized U.S. citizen from Lebanon, acknowledged that his figures may not be entirely accurate. But he continues to repeat them on TV interviews, from his city council seat and in response to e-mails regarding the rental ban.

"The 35,000 figure may not be accurate, but it's a good indication," Abed said Friday. "It could be more."

The U.S. Census Bureau apparently contradicts Abed's assertion.

There are about 28,800 foreign born residents in Escondido, according to the 2005 American Community Survey released by the Census Bureau. The figure includes both legal immigrants and illegal immigrants.

About 39,600 of Escondido's 133,000 residents in 2005 were foreign-born, according to the Census Bureau. About 10,700 of the city's foreign-born population were naturalized U.S. citizens.

Paral was commissioned to produce his study by the nonprofit, pro-immigration American Immigration Law Foundation, based in Washington. The study said that, based on national figures, the population of foreign-born people in the United States roughly breaks down to about a third who are citizens, about a third who are legal residents and about a third who are illegal immigrants.

If those nationwide rates hold true for Escondido, Paral said, the number of illegal immigrants in Escondido may be much lower than Abed's estimate.

Not all immigration researchers agree with Paral's approach. John Keeley of the Center for Immigration Studies, a Washington immigration think tank that favors more stringent immigration controls, said Friday that it's impossible to estimate illegal immigrant populations in border towns and agricultural areas, where the population changes by the season.

"In border states, we see remarkable churn, with people coming and going all the time," Keeley said. He said he agrees with the national estimate that about one third of foreign-born people in the U.S. are here illegally, but that applying that trend to any one community is faulty demographics.

"I don't think you can portion it quite that way," he said. "There are so many factors at work."

Paral's study estimated that illegal immigrants make up about 6 percent, or about 42,000, of the 688,000 people who live in the 50th Congressional District. The district includes Escondido, San Marcos, Carlsbad, Encinitas, Solana Beach, Del Mar, parts of northern San Diego, and unincorporated parts of the county.

Under Escondido's rental law, the city would require landlords to provide proof that tenants are in the country legally. The federal government would verify the tenants immigration status. Only if the federal immigration officials say the documents are not valid would the city step in and require landlords to evict the tenants or face fines.

The law has bitterly divided the community.

Many have filled council chambers, rallied in front of City Hall and held candle light vigils at Grape Day Park. Many of them have also written e-mails to council members. Council members Ed Gallo, Marie Waldron and Abed, who voted in the majority to pass the rental law, pointed to the e-mails as evidence of community support.

Abed told Fox News that a large majority of the residents were in favor of the law, based on phone calls and e-mails city council members had received.

"The majority of the citizens, and it's over 90 percent, overwhelmingly supports our effort," Abed said.

By contrast, a North County Times review of the e-mails sent to council members dating from July 1, shortly before the rental ban was first proposed, to Oct. 5 -- after the first vote on the ordinance was taken -- indicates that the messages were about 72 percent in support of the ordinance to 28 percent against.

Of the more than 240 e-mails, many were copies repeatedly sent to several council members at once. Some were from people who do not live in Escondido.

In a city where about 42 percent of the population is Latino, Gerardo Gonzalez, past director of the National Latino Research Center at Cal State San Marcos, said the e-mails may not be an accurate measure of the community's feelings about the ordinance.

"You have to do more than read letters and e-mails" to gauge support, Gonzalez said. "You have to reach out to (constituents) to find out."

Contact staff writer Edward Sifuentes at (760) 740-3511 or esifuentes@nctimes.com.