The paintings of LS Lowry are unforgettable. That's partly because they can be reduced to such simple elements – Matchstalk Men and Matchstalk Cats and Dogs, as one-hit wonders Brian and Michael pointed out in a 1978 No 1 hit. But it is also because Lowry is a visionary who recorded the inner life of British cities in the 20th century more powerfully than any other artist.

They have gone now, the forests of tall, thin chimneys belching out black smoke, the crowds coming out of the factory gates in the evening, the Lyons cafes and pithead scaffolds. I can still remember the stench of sulphur mingling with the taste of fish and chips in a Welsh industrial town in the 1970s. Now British city centres are more likely to smell of Costa coffee. No wonder some would rather not remember Lowry.

Now it seems that the painter's champions, led by actor Ian McKellen, claim that the Tate is guilty of filing away and forgetting him. It owns 23 of his paintings, but apparently has only ever exhibited one of them, and that only briefly. McKellen challenges the Tate to either show these works or sell them, accusing them of anti-northern prejudice. "It is a shame verging on the iniquitous," McKellen says, "that foreign visitors to London shouldn't have access to the painter English people like more than most others."

Current building works at Tate Britain will allow it to do justice to its collection, we are promised, and the museum claims that Lowry, among others, will get his due. Yet in the meantime, its displays currently go deep into 20th-century art history without a sniff of a Salford mill scene. But this is not because of any animus against the north: it is the result of a snobbery towards "naive" and popular art.