WASHINGTON — Senator Rand Paul of Kentucky acknowledged Tuesday that “mistakes” in his office had caused unattributed writing by others to appear in his own work and announced that he was instituting safeguards to prevent such breaches from happening again.

While maintaining the defiance he has shown since the claims of plagiarism were first made last week, Mr. Paul hurriedly took steps to contain the biggest crisis of his young political career, one that threatens his ambitions to run for president in 2016. He said he was putting in place a more diligent system within his office to footnote and attribute material, part of what he called a restructuring on his staff. He said there would be no firings.

But, in an interview at his Senate office complex, Mr. Paul said he resented implications from those he termed “haters” that he had sought to dishonestly take other people’s work as his own. Facing a cascading series of accusations that he used plagiarized material in speeches, an opinion article and a book, he said the lapses were the result of his newfound status as a freshman senator in high demand, and the overwhelming workload that has brought with it for him and his staff.

“What we are going to do from here forward, if it will make people leave me the hell alone, is we’re going to do them like college papers,” he said. “We’re going to try to put out footnotes.” He said that “we have made mistakes,” but that they had “never been intentional.”