(CNN) The new US ambassador to the Netherlands, who was confronted last month by a Dutch reporter with comments he made in 2015 about Islamic "no-go zones," repeatedly made unsubstantiated claims about the nature of Muslim communities in Europe and pushed a hardline view of Islam, a KFile review of his public appearances and writings shows.

Pete Hoekstra, a former 18-year Republican congressman from Michigan who served for several years as chair of the House Intelligence Committee, was nominated by President Donald Trump last July to serve as ambassador to the Netherlands and confirmed by the Senate in November.

After leaving Congress in 2011, Hoekstra in 2014 joined the Investigative Project on Terrorism, a non-profit group that describes itself as the "world's most comprehensive data center on radical Islamic terrorist groups."

A KFile review of Hoekstra's time with the group reveals he claimed on multiple occasions that there are "no-go zones" in European cities and speculated as much as 15% of Muslims are extremists, a number that totals 270 million. He also promoted conspiracy theories asserting longtime Hillary Clinton aide Huma Abedin had connections to the Muslim Brotherhood and said he considered the possibility that then-President Barack Obama was allowing radical Islam to proliferate on purpose.

Hoekstra was also a frequent guest on a radio program hosted by Frank Gaffney, an anti-Muslim conspiracy theorist based in Washington who warns of the "creeping" influence of Sharia law worldwide.

Hoekstra drew criticism last month for denying in an interview with the Dutch news program Nieuwsuur that he made comments in 2015 asserting that there are Muslim-controlled neighborhoods in Europe that are so dangerous that non-Muslims cannot enter.

There is no evidence to support claims of so-called "no-go zones" in Europe. In 2015, Fox News had to issue an apology and a correction for comments made by a pundit on its air claiming the existence of such zones across Europe. That pundit was Steve Emerson, who runs the Investigative Project on Terrorism where Hoekstra served as a fellow.

Hoekstra apologized for initially denying he made the remarks in the interview with Nieuwsuur, writing in a tweet that he looked "forward to the opportunity to learn, to listen and to move on in the spirit of peace and friendship with the people and the leaders of the Netherlands."

Reached for comment, a spokesperson for the State Department pointed to Hoekstra's earlier statement on Twitter. A representative from the White House did not respond to a request for comment.

No-go zones:

Hoekstra has made false claims about "no-go zones" several times. In a 2016 radio interview, he told Gaffney, "You know there are no-go zones in Europe, areas that you know law enforcement and civil society by the government cannot be enforced, and you know they have become safe havens and sanctuary areas for the radical jihadist movement."

"They are places that, you're right, these groups can find safe havens. But at the same time, they have allowed the mosques to preach radical jihadism, so the mosques are training centers."

In a 2016 speech to activists in Colorado, Hoekstra said there are parts of Europe where Sharia law is allowed.

"Look at what's going on in Europe in large parts of, you know, in many parts of Europe there are, there are, there are little enclaves or areas where they allow for Sharia law," Hoekstra said.

On Islam:

In a 2017 radio interview, Hoekstra speculated that as much as 15% of Muslims could be radical jihadists, a number that would total 270 million. It's unclear where he came up with this figure.

"We should recognize that it is a radical jihadist, Islamic force that we face," Hoekstra said. "Whether it's 10% of the Islamic community or the Muslim community or whether it's 15% or whatever the percentage is, it's a significant number. We need to recognize that this is a threat from people who use religion to motivate their followers, to recruit their followers, and those types of things."

Hoekstra has also derided past US presidents for calling Islam a "religion of peace." In one video with activist Ginni Thomas in 2016, he said it is "clearly not true" that Islam is a religion of peace.

"I mean you hear former President Bush and President Obama now for what 15 years telling us, 'Islam is a religion of peace,'" Hoekstra said. "The average person on the streets says, 'whoa there.' See they're beheading Christians, there's you know, there are suicide bombers, they're taking gays and lesbians and throwing them off the top of buildings, and they're selling women into sex slavery. That doesn't kind of look like a religion of peace to me. Now that's not all Muslims, but that's that's what a lot of people are saying. So then they ask the question to say well why would our President be telling us this. It's clearly not the truth."

Referred to Middle East refugees as "invaders:"

Hoekstra twice-referred to refugees from the Middle East as "invaders" on a far-right radio show.

"We took a stable part of the world and we turned it into an ungoverned region that is now exporting fighters and weapons and refugees or invaders into Syria, into Iraq, and into southern Europe," Hoekstra said during a discussion about US involvement in Libya.'

"The Muslim population has been shown ineffective in terms of integrating them into our culture and to really becoming German. And the third thing is ISIS and other groups, and we know this very clearly, they know they have infiltrated the refugees or invaders, whatever you want to call them. They are part of the folks coming," he added later in the broadcast.

Spread false claims about Huma Abedin:

At a 2016 conference hosted by Brigitte Gabriel, an anti-Muslim activist whom he has praised and said he was working with, Hoekstra said that Huma Abedin, a top aide to Hillary Clinton, had "egregious" ties to the Muslim Brotherhood but added there were better examples that connected the US government to the group.

Claims that Abedin has connections to the Muslim Brotherhood have been labeled as false and unfounded by fact-checkers from the Washington Post PolitiFact , and Snopes

"We need to recognize that a lot more has come out about Huma and a lot of this stuff has been known by the Investigative Project on Terrorism, and I've talked with Steve (Emerson) about this extensively. We don't believe, as egregious as what Huma Abedin and her connections and her family are, again it's why we're doing what we've done, the research, we think there are much better examples of making the connection between the US government and this administration and their connections with the Muslim Brotherhood," Hoekstra said.

Hoekstra also shared an article on Twitter that made the unfounded claims , calling it "worth a read."

Said he had considered President Obama might be aiding rise of radical Islam on purpose:

In an appearance on a far-right radio show Tru News in 2015, a host asked Hoekstra if he had considered the possibility that Obama was intentionally trying to create safe havens for jihadists.

"I've considered that possibility," Hoekstra answered. "That is a frightening thought that we would have leaders in our government who would actually want to create a safe haven for radical jihadists, but that is in effect, what they have done and it's the result of Hillary Clinton's policies that have created an arsenal of weapons and the training ground for jihadists."

The host later added that he was "firmly convinced" that it was Obama's "desired strategy."

"His policies have created an environment where radical jihadism has flourished, is worse on the Arabian peninsula," Hoekstra said. "It is flourishing in Syria and Iraq, Turkey, and it is flourishing in northern Africa. I was just in Europe a couple of months ago, still have a lot of contacts in Europe. You know the people of Europe are frightened about what to Europe with this mass infusion of people from the Middle East and this president is doing nothing to stabilize or control the events that are going on. Either he's facilitating, as you would argue, or he's standing on the sidelines as this is happening."