Courts that are like an A&E unit on a Saturday night, violent abusers walking free because evidence has gone missing, and lawyers doing hours of unpaid work to keep the system from collapse, are all part of a damning picture painted in a new book on the legal system by a barrister.

According to the anonymous author of The Secret Barrister: Stories Of The Law And How It’s Broken, the courts in England and Wales have been brought to their knees by government cuts and left so plagued by daily errors they are no longer fit for purpose.

The identity of the writer of this fly-on-the-wall account of what goes on in courtrooms across the country is a well-guarded secret – and the subject of online curiosity among a Twitter following of 87,000.

The eponymous “secret barrister” uses the accounts of real people and cases to reveal the legal system as being so broken that the innocent can find themselves behind bars while “every single day the provably guilty walk free”.

In a newspaper interview the author, a criminal barrister who works as a defence lawyer and prosecutor, warns that our legal system is approaching a tipping point and in urgent need of funding and reform.

From the “wild west” of the magistrates’ court, likened to “an inner city A&E department on a Saturday night” to the upper echelons of the crown court, where the stakes are higher but the catalogue of errors equally long, the author describes a system creaking under the strain of a decade’s worth of cuts.

Amid speculation and intrigue over the identity and gender of the author, some rumours have suggested that the hugely popular blog is an algorithm run by a small section of the legal community.

“Secret barrister” has said that just close family members are privy to this moonlighting. “I don’t have a profile outside my online existence. I’m a junior criminal barrister, I’m extremely ordinary. I hope the focus of the book will be on the issues raised rather than me.”

The book says: “Walk into any court in the land, speak to any lawyer, ask any judge, and you will be treated to uniform complaints of court deadlines being repeatedly missed, cases arriving under-prepared, evidence being lost, disclosures not being made, victims made to feel marginalised, and millions of pounds of public money wasted.

“I wanted to bring the things I saw that upset me to a wider audience. They will not come as a shock to lawyers in the system. But whenever I [spoke] to a non lawyer about them they would look at me with horror and I realised there was a disconnect between the criminal justice system and the people it is meant to serve.”

The book tells the story of a man held wrongly on remand for months on end, a violent abuser allowed to walk free because basic evidence was missing and a vulnerable witness who gave up after a trial was adjourned for a third instance due to lack of court time.

Defendants, victims and ultimately society are failed on a daily basis with life-changing consequences, the author claims, by a system brought to its knees by years of public service cuts.

The barrister cites the problem of repeated court adjournments and issues around disclosures as two of the toughest challenges for the system. But, overwhelmingly, the biggest problem is lack of funding across the board, the writer says. “The system is at breaking point and now running exclusively on the goodwill of the barristers and solicitors that work unpaid, after hours, through lunch, through nights, through weekends, to plug the problems in the system. Perhaps we need to say if we, the court staff and the CPS staff weren’t going the extra mile, if judges weren’t above and beyond, then everything will collapse.”

There is also a warning that, with changes on the horizon concerning the way criminal barristers are paid, there may come a tipping point soon. “There is a lot of disquiet because reforms the government insist are cost neutral, upon inspection don’t appear to be. They will continue to push people out of the profession.”

However, for the moment, the secret barrister will not be among those departing. “People do not go into criminal justice for an easy life or because they want to earn a fortune but because they want to provide a public service and see justice done.”

But there is one vital half of the job that remains undervalued and misunderstood. “It’s curious, the question that comes up without fail, when I’m asked what I do for a day job – how can you defend somebody you know is guilty? But I’ve never once been asked by anyone – how can you prosecute someone you think is innocent?”

People in Britain tended to lean towards the presumption of guilt rather than innocence, the barrister suggested. “The same cognitive bias that a lot of us share and is not helped by the way the tabloids treat criminal justice, which is – there is no smoke without fire.”

There was a tendency, too, to overlook the word “accused” despite many first-time entrants to the justice system being innocent. “It doesn’t really stick with people until they’ve been through it personally or until they watch Making a Murderer on Netflix. A charge is not proof of guilt. People think it won’t happen to them, but anyone can find themselves in the criminal courts. You never know when you might need a good lawyer and if you do you’d better hope they are operating within a system that works.”

The Ministry of Justice and the Crown Prosecution Service were approached for a response but declined to comment.