Washington(CNN) Nearly a year into President Donald Trump's administration, senior-level staffers -- including Ivanka Trump, Jared Kushner and Rob Porter -- remained on interim clearances even as other senior advisers were granted full security access, according to information obtained by CNN from a US government official.

Having interim clearance can hamper a staffer's ability to perform essential functions of the job, a former administration official said. It requires those with full permanent clearances to remain vigilant about what information is shared with those still operating on an interim basis.

There were more than 100 staffers in the Executive Office of the President who were operating on interim clearances more than a year after Trump was elected, according to the information.

It's not clear which of those staffers gained full clearances in the three months since the information was produced in November. It is also unclear whether the delay is the result of a bureaucratic backlog or potential complications in the background of these aides.

At least two dozen of the staffers with interim clearances started working on the first day of the Trump administration, according to the information.

Some officials who started on January 20, 2017, and were without permanent clearances by November include a special assistant to the president for national security affairs and the National Security Council's senior director for international cybersecurity.

Officials familiar with the process have said complicated background checks and a backlog at the start of an administration have slowed the clearance process.

Former congressman Mike Rogers, a Republican who chaired the House Intelligence Committee who has been critical of the Trump administration, said this White House's security clearance policies do not serve the country well.

"The security clearance process is critical to keeping America's secrets," he told CNN. "Foreign intelligence services look for vulnerabilities in individuals with access to our most sensitive information. Not following the process is a disservice not only to the individual but to our countries security interests."

"It's unusual that so many have taken so long," he said.

The White House has declined to publicly detail the security clearance process or say which officials are operating on interim or full clearances. The White House did not respond to CNN's requests for comment.

Paul Light, a New York University professor who is a government bureaucracy expert, said it seems in some cases a "temporary" status ends up meaning "semi-permanent."

"The problem is that these temporary authorizations are lasting longer, or appear to be lasting longer, and that exposes the nation to security risks that we shouldn't have to bear," he said.

Chief economic adviser Gary Cohn, presidential counselor Kellyanne Conway, personnel director Johnny DeStefano, communications director Hope Hicks and policy adviser Stephen Miller had all received full top-level clearances by November, according to the information.

That stood in contrast to aides of similar stature who remained only on interim clearances. The information indicates the President's daughter Ivanka and her husband Kushner, both serving as senior advisers, were operating with interim access to Top Secret information, as well as Sensitive Compartmented Information (SCI), in November. Ivanka Trump joined the administration in March, while Kushner joined when Trump entered office in January 2017.

Top-secret information is defined by the government as anything that, if disclosed unauthorized, would cause "grave damage to the national security." Sensitive Compartmented Information is defined as classified information that's derived from sensitive intelligence sources or methods.

Porter, who served as Trump's staff secretary since he entered office last January, was also on an interim clearance for both top secret and SCI.

Some others had been approved for permanent access to top secret information but were still working off interim access to Sensitive Compartmented Information. That included Don McGahn, the White House counsel, and Sarah Sanders, the press secretary.

The matter of clearances has gained renewed attention after Porter's resignation. On Tuesday, the FBI director said during congressional testimony that his agency had raised issues with Porter's background to the White House at various points over the past year. He nevertheless remained in his post until news outlets detailed his ex-wives' accusations last week.

Porter's replacement, Derek Lyons, was also operating on an interim clearance in November, according to the information obtained by CNN. Lyons served as the deputy staff secretary since the start of the administration.

People familiar with the clearance process have said that staffers who are very wealthy or worked in areas of finance with ties to foreign nationals and governments would also contribute to a delay in the clearance process. Cohn, however, served as president and chief operating officer at Goldman Sachs and still obtained a full clearance by November.

Kushner's lack of a full clearance has come under scrutiny because of his involvement in a variety of national security matters. His attorney, Abbe Lowell, said in a statement this week "it is not uncommon for this process to take this long in a new administration."

Lowell stated there are "a dozen or more people at Mr. Kushner's level whose process is delayed like his."

Other notable staffers, like former NBC "Apprentice" star Omarosa Manigault-Newman, who has since left the White House, had no security clearance nor applied for one.