Here’s an austerity drama made with the best of intentions on what looks like the thriftiest of budgets; so low-budget, in fact, as to almost be homemade. It’s about the plight of carers, beginning straightforwardly enough in social realist mode with frazzled full-time carer Sadie (Shian Denovan) and her disabled sister Emily (Meg Fozzard) struggling to get by. The government is introducing new welfare reforms that will make their lives harder still, but Sadie is too exhausted to join the protests. Then, as if Ken Loach were put in charge of the Ocean’s Eleven franchise, the plot takes a lurch into heist movie territory, with Sadie cracking a plot to break into parliament.

Enter government minister Michael Harrington (Tom Knight). He’s an MP in the silver fox tradition – very posh, all eyebrows. He is suffering an attack of conscience over the new legislation. But before Harrington can resign, he gets the boot from chief whip Damian Wilson (Ray Bullock Jnr), a smirking creep who keeps in his safe a little black book filled with dirt on his party’s MPs. When Sadie watches a news segment about Wilson, she decides to steal the black book, leak it to the press and bring down the government.

Within five minutes of walking into Harrington’s constituency surgery, she has recruited him to her heist. This, to be fair, is not the most sizeable implausibility here. And there are a couple of performances that feel more wooden than the panelling in the chief whip’s office. But the film, directed and co-written by Christopher Presswell, is likable enough – though I was puzzled as to why Emily, the only character with a disability, appears in just a handful of scenes. The film opens with the humiliating ritual of her being assessed for her Pip, the personal independence payment. But she is then sidelined, in what feels like a wasted opportunity to present disabled characters on screen.

• The Whip is in UK cinemas from 4 September.