Of all the reasons there are to love Barbra Streisand – and if you find that proposition contentious, I encourage you to stop reading and do something else – the quickest and easiest can be found in the answer she gives to the first question I ask her. Streisand, speaking on the phone from her home in LA, is about to release Walls, her first album of primarily original songs since 2005 and for which she has written the bulk of material. The lyrics are sharp and political, the arrangements are strong, but it is the vocals that are the most surprising: crisp, forceful, with none of the mellowing one might expect of a 76-year-old artist who on recent albums has seemed muted. I mention this to her – how great she sounds – and she bursts out laughing and says: “I know! I swear to God, I don’t know where my voice came from. I would come out of the studio and [the technicians] would go, ‘How the hell?’ And I don’t know, I don’t know! It just came out of me!”

One doesn’t look to Streisand for modesty, of course, but there is something deeply gratifying, in this moment of heightened alertness to female social conditioning, about the fact that she has never once been known to demur. Streisand does not do little-me-ism. She is – in the language most people now recognise as coded to undermine women – strident, abrasive, political in a way that frequently upsets or prompts the rolling of eyes. In her art as in life, she can be very, very loud.

And of course it has garnered much ridicule. If Streisand was outlandish in the 1960s, dressed in a misshapen fur coat with three-inch fingernails and insane eye makeup, that image has only consolidated over the course of five decades, two Oscars, 68m album sales and eight Grammys, so that in large areas of the popular imagination she continues to be an absurd creature, indecorously out of line with how women should be. (This is also the source of the wild devotion she inspires; as a 20-year-old exploding out of the nightclub scene in New York, she seemed to many women, my mother included, to expand the range of how they might successfully be.) A week before the interview, I am at a dinner in New York when Streisand’s name comes up and a male guest snorts and makes a derogatory remark, whereupon the eyes of every woman in the room swivel coldly in his direction. “The Way We Were is one of the greatest movies ever made,” I say stiffly; back we swivel, as one. With everything else going on, this is not the moment to tangle with us on Babs.

And it’s true about The Way We Were. There are a lot of turkeys in Streisand’s filmography – The Main Event, Nuts, All Night Long (you can argue the toss on Yentl; personally, I’m in favour) – but along with Funny Girl and Hello, Dolly!, The Way We Were stands iconic in US film history. Streisand should have won the Oscar for it in 1974 – instead it went to Glenda Jackson for A Touch of Class – and it is assumed that she lost, in part, because of the film’s confused final edit, in which its lefty politics were toned down by the studio. More than 40 years on, though, she has complete creative control and can be as political as she likes. And so here it is: an album that is a well manicured middle finger to the 45th president of the United States.

Nowhere in the album is Trump mentioned by name. “You have to write lyrics that can be more than just a protest,” she says. “They have to appeal to a universal audience. Even when I wrote Don’t Lie to Me, at first I thought, well, I could make you think it’s like a love affair, a marriage breaking up. It’s a universal thought: don’t lie to me.”

She is not, however, talking about a love affair. As the video for the song makes clear (“I couldn’t help it!”), she is talking about Donald Trump, who flashes up on screen and about whom, over the course of our conversation, Streisand is by turns calmly analytical – issuing measured statements rustled up by background assistants from her blogs and tweets – and intemperate. “I can’t bear the man!” she says at one point, her voice rising up to the roof. “He’s a man with no manners! He doesn’t see his own flaws; he doesn’t know what he doesn’t know. You know? He has no humility.” He is, she concedes, “good at marketing. He knows how to sell; he’s a conman. That’s what he’s good at. But he doesn’t think he needs anyone’s help, he thinks he can go it alone.” She adds, drily: “The big guy.”

Walls is not a concept album, but it is the first album in which Streisand has linked the songs with a broad theme – the danger Trump poses to the country she loves. “This is what’s on my mind,” she says. “This is a dangerous time in this nation, this republic: a man who is corrupt and indecent and is assaulting our institutions. It’s really, really frightening. And I just pray that people who are compassionate and respect the truth will come out and vote.” Actually, she says: “I’m saying more than just vote. Vote for Democrats! Vote for what they want their country to look like and feel like and be like. And treat each other with kindness and respect – I have friends who are Republicans and we have dinner and agree to disagree.”

But surely they are not Trump supporters? “They don’t like Trump. They like other aspects of being a Republican. About two weeks ago, I had a call from Senator Bob Dole and he wanted to tell me how much he enjoyed my music and it was just so sweet of him, he’s 95 years old. And we talked about Trump! I don’t want to put words into his mouth, but we talked about when people are fair and open-minded, they can walk across the aisle. That’s what life should be about, where people communicate and agree to disagree with kindness and respect. And we’re losing all of that. I wish we had a gracious president who had compassion, someone who doesn’t have to insult his opponents or make fun of people with disabilities, or can take criticism without lashing out.”

It is highly risky to flood an album with politics, not just because you may alienate 50% of your audience, but because it can give the whole thing a pinched air of agitprop. This hasn’t happened with Walls. Apart from the Broadway covers, I don’t listen to anything Streisand has made more recently than Guilty (1980) – it took me a long time to recover from her collaboration with Céline Dion – but this album will change that. Don’t Lie to Me has a feel of William Orbit-era Madonna about it; the few covers – including a blend of Imagine and What a Wonderful World – are largely successful. And the politics, rather than cramping her style, seem to have unleashed something of the old Babs, the holy terror who would insert wild outbursts into her songs and who, over the years, has tended to be buried beneath rose petals and whimsy.

Facebook Twitter Pinterest Streisand receives the Presidential Medal of Freedom from Barack Obama in 2015. Photograph: Alex Wong/Getty Images

In fact, says Streisand, the whole exercise has been a release. “The first words I ever wrote about this album on a little piece of paper were: ‘Up is down, wrong is right, facts are fake, and friends are foes,’” she says. “And that became part of The Rain Will Fall. What [Trump is] doing is reversing reality, actually. It’s like that joke: a woman walks in and her husband is in bed with another woman. And he says, ‘Who are you going to believe, me or your lyin’ eyes?’

“Facts matter,” she continues. “Words have meaning. This man defies that. He says climate change is a hoax. Let’s release more coal and carbon into the air and have more megafires and hurricanes. I mean he’s so stupid! He’s so ill-informed. Liar is not enough of a word. There must be a bigger word for someone who lies about everything.”

The Rain Will Fall has an anthemic quality about it, full of foreboding that, Streisand says, she “meant as prophetic. I meant it as if the word were spelled ‘reign’. In other words: [Trump] is like Humpty Dumpty, a fat egg, sitting on a wall, and one day he’s going to fall off the wall. And crack.” It is impossible to convey quite how much disdain she packs into the words “fat egg”, but it is so heartfelt we both burst out laughing.

Given Trump’s propensity to slam his enemies on Twitter, is she anxious he will come after her? “I know that’s a possibility. Maybe he doesn’t think I’m powerful enough. I’ve seen him in the film of people in my audience … maybe he’s a big fan!” She laughs. “I don’t know. That’s the chance you take. Whatever. The country is more important to me at this point than whether my album sells. I’m sure Don’t Lie to Me turns off a lot of people who are Republicans or rightwingers. But there are some good Republicans! I was friendly with John McCain. I’m friendly with Colin Powell.”

Her greatest political allies in recent years have been the Clintons. Streisand was a prominent supporter of Hillary and, before that, Bill. She clearly identifies with Hillary as a woman attacked less on the specifics than for what she represents. She won’t be drawn on whether Clinton should run again, however. (The only other thing she won’t talk about is the Lady Gaga-led remake of the 1937 film A Star Is Born – a version of which Streisand starred in with Kris Kristofferson in 1976 – about which she has been scrupulously polite.)

Facebook Twitter Pinterest With Kris Kristofferson in A Star Is Born. Photograph: Allstar/Warner Bros

She says what happened to Hillary “really kills me. Years ago I gave a speech about language and how women are described compared to men. You know, he’s assertive, but she’s aggressive. He’s commanding, but she’s demanding. And it really applied to Hillary Clinton. It has been said that a man’s reach should exceed his grasp. Why can’t that be true for a woman?”

This is a question with which Streisand is intimately familiar, as is the notion “that men and women are measured by a different yardstick. And this makes me angry. Of course, I’m not supposed to be angry. A woman should be soft spoken! Trump raises his voice, screams at the top of his lungs, and they’re fine with that. A woman has to be something else. I think they just didn’t want a woman to run the country. And women get jealous of other women, or feel less-than compared to her experience. Remember when he said she doesn’t look presidential.” Streisand’s accent takes a sharp turn towards the Brooklyn of her youth. “He looks presidential?” she says. “With that hair and that makeup?”

Since the release of Streisand’s first album, in 1963, her ambitions have been considered almost extraterrestrial in scale. “Well, yeah. I didn’t want to stay in my place. I started out wanting to be an actress and I got to acting through my singing. But then that wasn’t enough. I wanted to shape things, I wanted to write. I wanted to direct. I wanted to produce. I wanted to make decisions. And that got me into trouble. A woman in control: that scared men. It scared other women! They weren’t ready for it.”

Did she bite her tongue when criticised? “Well, I didn’t. That’s my problem. I would constantly get attacked; I still get attacked. I remember a line from George Bernard Shaw’s play Saint Joan: ‘He who tells too much truth shall surely be hanged.’ I was making TV movies about subjects I loved, about gun control, gay rights, about Margarethe Cammermeyer, who was ousted from the army for telling the truth about her sexuality, and that didn’t make me more popular with a lot of people. But it’s what I believe in my heart is what decency is, and fairness. So that’s what I stand up for.”

But you’re a human being; you must still have had failures of nerve. “Oh yes, I do. I’m scared to go on stage! I still have stage fright. What’s that about? I’d love to do more concerts, and go and sing my new songs, but it’s kind of traumatic for me.”

What do the therapists say? “I’m not in therapy. That was a long time ago.” Therapy for Streisand these days comes down to a question of lifestyle. “I enjoy my private life; I enjoy bidding on auctions; collecting art; I don’t enjoy writing my book, but I’ve been working on it for the last four years and have got to get it finished. I enjoy my privacy; I enjoy my garden. I have 800 rose bushes. I enjoy the search for beauty.”

Facebook Twitter Pinterest ‘I have 800 rose bushes. I enjoy the search for beauty.’ Photograph: Russell James

The last track on the new album is Happy Days Are Here Again, a totemic song for Streisand that appeared on her first album and that she has been singing ever since. That first recording has a finale in which Streisand spins off into a scream and that, at the time, she intended “to be like the end of the world – this was around the Cuban missile crisis – because maybe we’re going to be blown up by nuclear weapons”.

This version is different; it collapses down into a whisper and she seems almost to be crying, a decision that still slightly mystifies her. “I did it several times and thought, Jesus.” Her inspiration was Mahler, “especially Symphony No 10, and I wanted to do a Mahler-esque version of Happy Days, because he was deeply sad, he had lost his wife when he wrote that, with the combination of the beauty of the orchestra and this great despair written into it. I remember thinking: I’m going to end the album with that.”

In fact, the final moment of the album is something else: a long sigh. “That final sigh!” she laughs. “When I first did it, people went: what? We’ll cut that out. I said: No, no, no, no, no. That tells the story. That tells how I’m deflated. I didn’t plan on doing it, but when it came out of me, wow.” In a highly partisan production, it feels like a universal note of despair. “That was the truth.”

Walls is released on 2 November on Columbia Records