This animated Netflix adaptation of Roald Dahl’s The Twits is only fractionally less gruelling than eating wormy spaghetti or finding a toad stuffed in the bottom of your bed. Dahl’s story about one of the most dysfunctional marriages in fiction is not exactly burdened with plot: the 95-page original is essentially a series of mean pranks, all monstrously mangled here and tortuously added to.

There has been some outrage that Netflix have Americanised the story, but that is the least of this film’s problems. In the fictional city of Triperot, Mrs Twit (voiced by Margo Martindale) is a Texan in blue denim cowboy boots, unhappily married to Mr Twit (Johnny Vegas, keeping his Lancashire accent). The couple have built a rickety amusement park called Twitlandia, with rides made out of toilets and old mattresses, all powered by the magical tears of the Muggle-Wump monkeys. When authorities close down the amusement park on the grounds of health and safety, the gruesome twosome go to war with the city.

The story is flabbier than Mr Twit’s tum-tum, which is a shame since it was produced, directed and co-written by Phil Johnston whose previous credits include clever and imaginative family animations such as Wreck-it Ralph and Zootopia. In an appalling mangling of Dahl’s story, the Twits flood the city with rancid hotdog meat before deciding to run for mayor. And ordinary working people are suckered in by the Twits’ pledge to make Triperot great again, in a frankly age-inappropriate satirising of the current state of politics.

Any of Dahl’s gruesome sense of fun is obliterated by a bulldozing message of empathy and kindness, thanks to a plucky orphan Beesha (Maitreyi Ramakrishnan) and her pals pulling together an opposition to the Twits. This is vile and revolting in all the wrong ways.

• The Twits is on Netflix from 17 October.