'Some people just shouldn't have children,' goes the old snobby saying. Debut writer-director Fyzal Boulifa tests the limits of the liberal response to that, with a film that features irresponsible parenting and its catastrophic results. However, what he's really interested in is the haste and heartlessness of the judgements which follow, with vilification spreading through a working-class community like a virus.

Now in their late twenties, neighbours Lynn (Roxanne Scrimshaw) and Lucy (Nichola Burley) have been inseparable since the age of 11. We meet them at the baptism of Lucy's first child, where the boy's disinterested father Clark (Samson Cox-Vinell) is glued to his phone. A mother to a 10-year-old herself, Lynn makes a proud and loving godparent, but cracks in her and Lucy's co-dependent relationship are visible from the outset; insecure and somewhat lost, Lynn eyes her glamorous, more confident friend a little jealously, and witheringly when she's worse for wear. We watch Lynn nervously apply for what will be her very first job – as a trainee hairdresser, humiliatingly hired by an old school adversary – while Lucy struggles with motherhood, before a terrible incident brings things to an ugly head.

Filmed in Harlow, Essex, though its stark, fable-like morality tale could be set anywhere, Lynn + Lucy is inspired by true events. Shooting with a fixed camera and with the action narrowly framed, Boulifa wants you to scrutinise the characters' responses and reactions throughout, as Lucy becomes an unmistakable pariah – sporting a silver puffa and with green-blue hair – and Lynn turns her own proximity to tragedy into horrifying currency at the salon where she works, forming the most fragile of alliances with bitchy manager Janelle (Jennifer Lee Moon) and the apparently more sensitive Caroline (Kacey Ainsworth, best known as Little Mo from EastEnders).

Unshowy in her credibly wrought anguish and making for an intriguingly blank slate, Scrimshaw was street cast and her triumphant performance is complemented by similarly unaffected and enigmatic turns, including from an excellent Burley (Wuthering Heights, Love + Hate). It can be hard to stomach how close to reality this all is but, in its knotty and confrontational treatment of the material, Lynn + Lucy is a thought-provoking, worthy watch that asks us to see the human beings behind the headlines and consider the consequences of our words.

Available to watch on BFI Player from Thu 2 Jul.