(CNN) -- Republican presidential hopeful Mitt Romney on Tuesday fired a landscaping company that worked at his home in Boston, Massachusetts, after he said he learned it employs illegal immigrants.
Mitt Romney sparred with Rudy Giuliani over illegal immigration during the CNN/YouTube debate last week.
"I am disappointed that our relationship must end on this note," Romney wrote in a letter to the company that was released by his campaign.
"But we simply cannot tolerate your inability to ensure that your employees are legally permitted to work in the United States."
With the former Massachusetts governor locked in a tight race for the top spot in the GOP's upcoming Iowa caucuses, the company -- which Romney said he gave a "second chance" after similar concerns arose last year -- had become an easy target for his political opponents.
"The company's failure to comply with the law is disappointing and inexcusable, and I believe it is important I take this action," Romney said in a written statement.
Romney said he met with the owner of the Community Lawn Service last year and agreed to keep using it after the owner guaranteed him he would only hire legal workers.
Tuesday's announcement came after the Boston Globe approached the campaign with what an official called "credible information" that the company continued to employ illegal workers -- including some at the Romney home.
Immigration reform is a major topic in the race for the Republican nomination, with candidates working to position themselves as tough on workers entering the country illegally.
During a CNN/YouTube debate last week, former New York Mayor Rudy Giuliani attacked Romney for living in a "sanctuary mansion" where illegal immigrants were allowed to work. Watch the Giuliani-Romney exchange »
Romney clarified that it was the company, not him, that hired the workers and called it "offensive" to suggest he should have checked their immigration status.
"Are you suggesting ... that if you have a company that you hired to provide a service that you are now responsible for going out and checking the employees of that company, particularly those that might look different or don't have an accent like yours?" Romney said during the debate. "I don't think that's American."
On Tuesday, the Giuliani campaign said "the Romney statement speaks for itself" and offered no further comment. E-mail to a friend