Agirl in voluminous skirts wrestles a dog to the ground. It lies on its back, startled and gasping, helpless as the poor mutt submitting to heavy chains in the neighbouring painting, or the dog having its throat shaved with an open razor in the next. A fourth painting, very famous, shows another girl – though somehow it is always the same girl – apparently raising her dress to a dog that sits before her with uncomprehending obedience. The title confirms what your eyes can hardly believe; but what is really going on in this scenario? You are asked to look, imagine, identify; what is she taking out on these dogs, and why; what is the relationship between human and animal; is this a kind of bestial abuse? The dogs have a whole range of expressions, but the girl (no matter the variations in features, clothes or age) has only one. She is a vision of fixed determination. You will see this girl, and her many dark-haired sisters, all through Paula Rego’s lifetime retrospective at Tate Britain. To describe this show as stunning would be an understatement; the paintings of seven decades (Rego is 86) deliver a ceaseless bombing pattern of riddles and shocks. Here is The Policeman’s Daughter, thrusting her arm up the stiff column of his jackboot, vigorously polishing its surface – now who’s in charge? Here is The Little Murderess in her fetching green frock, flexing its matching sash between two fists to strangle some offstage victim. Above all, here is that frightening enigma, The Family. Set in the well-heeled backdrop of Rego’s own Portuguese childhood – all mahogany furniture, sturdy shoes and Peter Pan collars – this episode takes place in the bedroom. The father is having his trousers buttoned, or is it unbuttoned, by the eldest daughter. She forces herself between his legs. The mother, distinguishable only by her larger size, rips at his jacket while the youngest child presses her hands together in anticipation, as if waiting for her dad to be served up. Unless, of course, they are just searching his pockets to buy cinema tickets – an interpretation I once heard. All stories are true, all mysteries open in Rego’s art, and this is abetted by the picture-book aesthetic. Her narratives have the darkest undercurrents of violence, eroticism, oppression, even incest, and at the same time the look of children’s fables and proverbs. How she reached this point is a revelation of this show, which presents her political paintings from 1950 onwards. The opening image, in fact, shows a woman huddled in a chair between two faceless interrogators, one holding an electric drill. Rego grew up under Salazar’s fascist dictatorship; she made this painting as a brave teenager. But its conventional expressionism soon gives way to something wilder, with overtones of Dada, Picasso, Philip Guston. Weird figures are collaged with torn paper, torrid colour and outright cartoon. Her satire is republican, anti-clerical, Goya-esque. A child peers beneath a priest’s cassock: an empty tent of thin air. Eventually, the black outlines shape themselves to Rego’s familiar lexicon: the sturdy girls, with their stout shoes and capable forearms; the women with their beehives and 50s shapewear; the bestiary of naughty monkeys, hares and dogs. Wife Cuts Off Red Monkey’s Tail, Red Monkey Offers Bear a Poisoned Dove. Even if the wall texts didn’t insist upon the autobiographical details of Rego’s marriage to fellow artist Victor Willing, and their affairs, you would know the animals stood in for people. Willing appears twice in The Dance, painted just after his death in 1988. In this seaside dreamscape, figures twirl beneath a full moon; some are tiny, as if remote in memory or time; others sinister and vast. Willing dances once with his wife, and once with a blond woman whose back is turned to us. He sends a complicit glance our way. The painting is profoundly complex, yet stylised as the Disney cartoons that Rego admires for their probing of the collective psyche. And you should watch out for your subconscious in this show. A man in a kennel; a skull-headed scarecrow; the shocking barn scene in which a Disney princess lies face-down in the hay, frilly dress lifted to bare her bottom to two tiny women with raised whips. One has Rego’s own face, just to intensify the flinching recoil. These big paintings often pit little adults against muckle kids. Scale is always vital. The eponymous Cadet is a silly doll beside his big sister, overwhelming in her blood-red clothes as she tightens his boots. Bondage – physical, emotional, familial – is always in the air. It is not always clear who’s in control. You are not to look at her art and be lost in the way it is made. Rego bypassed aesthetic niceties long ago with her direct and urgent brushwork. Oil pastel gradually became her main medium, allowing for even more force, and in the 90s she began working with studio models. This can go two ways. The images made in response to Portugal’s 1998 failed abortion referendum are tragic masterpieces. A schoolgirl lies hunched on a bed, agonised after a backstreet abortion. Another clutches a cushion on the floor. A woman sits with her knees apart, face a rictus of pain, mouth tight shut so she doesn’t cry out as the bucket awaits. They must not give themselves away. The models’ bodily knowledge meets our own and counts in every work; and so the personal becomes political. These pictures were widely reproduced in the Portuguese press, helping to overturn the law. But the 2004 Possession series simply presents a model lying at various angles on a couch. We’re told to think of Jungian analysis, Rego’s depression and Charcot’s notorious 19th-century photographs of “hysterical” women, but it doesn’t help to animate these studio setups, which lack internal life and pressure. The comparison with Lucian Freud is, unfortunately, inevitable. The Tate wants to make an activist of Rego, and it is true that the radicalism of her early politics is there at the end, with paintings about human trafficking and genital mutilation. But the artist is ill-served by this reductive brief. Her gift is for the exact opposite: for deeply ambiguous and morally disturbing scenarios in which you are asked to think harder, feel more, be turned inside out. Ignore the captions and open yourself to the magical unease, the voodoo and catharsis of Rego’s art. The great works are by now classics, and perhaps none more so than the Dog Woman series from the 90s. Here, the people stand in for animals. A woman, destroyed by emotion, is living like a beast on the floor. She bays, defending herself against the next blow. She lies by an empty bowl. She sleeps on the jacket of her absent master. It is vital that the model is a real living woman, for these are not fantasies but incomparable truths about life and passion. And the artist, like the model, is entirely exposed: mouth open in a fearless howl.