A lack of social mobility in Britain’s “left behind” communities risks fuelling populism and becoming a national security crisis, according to Fiona Hill, the coalminer’s daughter who became a top White House adviser.

Hill, who was born in County Durham and went on to serve under three presidents and become US national security council director for Europe and Russia, warned that Britain’s social divide is so wide that some communities feel like “another world” to the cities.

The 55-year-old, who shot to prominence as a witness in the Donald Trump impeachment trial, where she described how her background and “very distinctive working-class accent” held her back in England in the 1980s and 90s said that class barriers today were still holding back people with regional accents.

Speaking at length for the first time about the social challenges in modern Britain, Hill said the same glass ceiling she faced four decades ago was still pervasive: “It’s still the same in many respects, the discrimination of accents … there’s still that kind of sense that you’re in another world”.

Hill said many people outside the big cities had been “left behind” in Britain, with a sense that “the rest of the UK doesn’t belong to all of the people who are from there”.

“It’s this lack of social mobility, all this grievance, that feeds into populism and it becomes a national security crisis over time, as we saw, because all of this can be exploited”.

Hill became the first in her family to go to university when she studied at St Andrews in Fife, then Moscow in the late 80s, before gaining a PhD at Harvard University. She joined a thinktank in Washington DC before becoming the top intelligence officer for Russia on the National Intelligence Council under presidents George W Bush and Barack Obama.

Her route out of poverty is described in a new memoir, titled There Is Nothing for You Here, in which she ascribes her unlikely success to luck, hard work and early government support.

In an interview with the Guardian, Hill said the prospect of taking out a student loan would make her think twice about pursuing her studies in today’s Britain. “It’s a very bad political moment for kids and with climate change and all the other issues. They’re also unlucky because the financial assistance has disappeared,” she said.

“A lot of people are making educational decisions based on what they can afford … So many people are discouraged from going on to higher education. This is the new marker of class, both in the US and in the UK. People say it’s culture or values – it’s education.”

Hill, who is from the market town of Bishop Auckland, is backing County Durham’s bid for UK City of Culture 2025, in part, she said, to show her gratitude to the council that funded much of her education in the 1970s and tuition fees at St Andrews from 1984 to 1989.

The county, which is in the top 40% of most deprived council areas in England, is one of 20 areas bidding for the title and the millions of pounds in investment that it brings. The Department for Digital, Culture, Media and Sport is expected to announce a long list of bidders within days, before announcing the winner in May 2022.

Hill, who was lauded as a “national treasure” for her precision and calm under pressure while giving evidence on Capital Hill, said her north-east accent – which would have “impeded my professional development” in England – was only ever mentioned by one president: George W Bush.

“He called me Blair’s girl because he was like: ‘Oh, where’s that accent from?’ and I said it’s from the north of England … just a little close to Tony Blair’s constituency,” she said. “After that he forgot my name but kept calling me Blair’s girl. I thought it was funny actually, I kind of liked it because he knew who I was.”

The author, who is now a US citizen but whose mother, June, still lives in County Durham, was critical of Boris Johnson’s levelling up agenda as being “driven by politics, partisan politics, and breaking the red wall”.

It “feeds into the idea that you have to be associated with the party in power to have anything turned around for you, or have policies focused on you,” she said. It was vital, Hill said, that local leaders were given real powers and money to drive change instead of policy being dictated from Whitehall.