Immigration advocates are criticizing California Democrat Dianne Feinstein over her proposed crackdown on so-called "sanctuary cities," Politico reported. Feinstein, the oldest currently serving the U.S. Senate, has said that she would soon introduce a bill forcing localities to comply with federal immigration requests or face cuts in appropriations.

The legislation would impact the 200-or-so jurisdictions across the country that do not allow municipal funds or resources to be used to enforce federal immigration, according to the Daily Signal. Most do so in an effort to support immigrants and provide assistance if they become involved with minor offenses.

Cristina Jimenez, the managing director of the immigration advocacy group United We Dream, harshly criticized Feinstein, who had long been considered a liberal ally in the Senate.

"(Her) bill is trying to get us to the point where we continue to generate fear at the local level," Jimenez said. "She is basically ... joining the Donald Trump bandwagon," the spokeswoman said in reference to the GOP presidential candidate's recent anti-Mexican comments.

Meanwhile, more than 50 groups have written a letter to Feinstein and fellow Sen. Barbara Boxer, D-Calif., warning the senators against measures they say would provoke fear within the immigrant community, Politico detailed.

Feinstein's proposed legislation came in reaction to the death of Kathryn Steinle, a San Francisco woman who in July was allegedly killed by an undocumented immigrant, according to CBS News. The suspect in the murder, Juan Francisco Lopez-Sanchez, had been in the United States illegally and had previously been deported to his native Mexico multiple times.

The incident also prompted some of the top Republican presidential contenders for the White House to call on local leaders to change "sanctuary city" policies, the network noted. GOP heavyweights including former Florida Gov. Jeb Bush, Florida Sen. Marco Rubio and Kentucky Sen. Rand Paul said the practice should be reconsidered.

"We ought to eliminate sanctuary cities," Bush argued, adding that the federal government "should not provide law enforcement monies for cities like San Francisco until they change their policies," according to Politico.