Robert Tressell's novel of 1914 possesses bitterness and real anger at the misery of his house painters' lives and the grinding inequality of the sharing out of the economic cake. The tragedy and gloom are shot through with a number of passages of comedy, but I don't think Howard Brenton, still going strong all these years since the 1965 premiere of his Ladder of Fools, has managed to resolve these elements into a coherent whole.

The Marxist analysis of capital and labour, the importance of the ownership of the means of production and the causes of poverty are earnestly expounded in two overlong chunks in the play, once by painter and pamphleteer Frank Owen and much later by colleague 'Professor' Barrington in a 'Pandorama' harangue. But Brenton fails to integrate these lectures into the narrative. This latter is never compelling, and when the socialist rhetoric makes its appearance, there's an almost audible crunching of gears and brakes as the drama stalls. Brenton's desire seems to be to emphasise the politics before the creation of character, but to my mind he compromises the seriousness of the message – and it could hardly be more vital; viz. the harrowing scene where Frank and Nora Own tot up their income, assets and debts – by the inclusion of almost cartoonish, vaudeville passages.

While colour and movement are supplied by songs, there are too many of them – one outburst early in Act 2 contained seven or so in a block – and while the audience around me was clearly relishing the first few numbers, by the play's end their appreciation had visibly tailed off. Nor is the language of the dialogue much more than flat. If a drama is to aspire to resonance beyond its specific time and place it may plausibly need to venture into the realms of heightened reality, perhaps with a touch of metaphor to spice up the exchanges. Brenton's wrapper device of a contemporary house-hunting couple landing on the very building that was to be the basis of the Boer war-era action felt redundant and in any case too short to achieve much resonance.

Director Ruth Readshaw does her level best to spice up the monologues with cast interpolations, lively backchat, jokes and hubbub. The Mugsborough Chamber of Commerce-types appeared in animal masks whose emblems of fat cats and - a jackal, was it? – as well as their names (Didlum, Grinder and Sweater etc) were unsubtle but fun. More interesting in dramatic terms is the establishment of foreman Hunter as simultaneously the workers' oppressor and the mouthpiece of the boss class, and of charge hand Crass who revels in his promotion and demonstrates his cyclical venality.

I know Richard Readshaw to be a skilled actor and here as the larger-then-life foreman Hunter he deploys an oily mix of aggression and shiftiness in a formidably booming voice, leavened by obsequiousness when dealing with his superiors. He boasts of his perk of 'taking 2½ % of the profits... for scamping down the costs' – human costs of course: his workers exploited and harassed, the paying house buyer cheated. But Mr Readshaw has to wrestle manfully with the problem faced by the rest of the cast, that Brenton's script creates little or no character development in almost any one of his characters.

I enjoyed Liz McHale's painter Bundy and business shark Rushton, brandishing a phallic cigar ('I'm thinking of driving down the [wage] rates'), her rasping voice and bustling presence creating a kernel of individuality. Tom Mason was an effectively low-key Owen, disseminator of political tracts and thinking, and achieved real force when saying of the foreman: 'This man has the power of life or death over us' – no idle hyperbole in this pre-Welfare State Britain. Chris Harris was a very sympathetic Old Joe Philpot, a veteran struggling against encroaching years and the knacker's yard, but a patriot: 'I've always been for England's wars!'.

Both Tobias Forbes, who has a fine voice and James Silk, a naturally attractive stage presence, did their considerable best with underwritten rôles. All three of the wives (Eloise Sheffield, Kirsty Ralston and Victoria Wilson) were authentically dressed, acted with poise and sang strongly in harmony. Daniel Taylor was a wide-eyed, lively figure.

At the very end we were treated to a visual coup; the appearance of one of those striking Trade Union banners that for a hundred years or more have adorned protest marches. This one was gorgeous in scarlet and a polychrome riot, beautifully expressing the pride of the downtrodden and the optimistic possibility of their achieving some sort of dignity if not equality. Ruth Readshaw and her dozens of associates have taken Tressell's burning novel and Brenton's flawed adaptation of it and created a production with a bit of fire in its belly and plenty of variation of spectacle. It's well worth catching this week at the Old Fire Station.