In the three weeks since the unveiling of the Paradise Papers, the government has clung to familiar arguments. These arguments have not been to do with the Panama Papers – the forerunner investigation into tax havens and offshore empires that the Guardian published last year. Instead, the echoes have come from another remarkable, though unrelated, case: the Edward Snowden intelligence leaks.

Four years ago I was part of the Guardian team trawling through thousands of classified documents that showed the inner workings of Britain’s GCHQ and its sister agency in the US, the National Security Agency.

In the weeks that followed the publication of our disclosures about the unreported extent of modern surveillance, there was a splenetic outcry from securocrats and (mostly) Tory MPs, indignant and enraged in equal measure that journalists had gained access to this private world. They accused us of treasonous behaviour. Instead of trying to answer the questions posed by the Snowden files, they tried to shut down any debate. “Where’s the wrongdoing?”, they asked. “Show us the illegality.”

GCHQ was working within the law – and the law was clear, they said.

One senior Tory MP assured me there was absolutely nothing in Snowden’s revelations – he knew this because the head of GCHQ had told him so. And that was that, as far as he was concerned.

The then foreign secretary, William Hague, said any suggestions GCHQ had done anything wrong were “baseless”.

A few months later, the debate had changed. Even those who considered GCHQ’s work to be beyond reproach were having to concede that the laws setting the parameters for surveillance were hopelessly inadequate and opaque, and the scrutiny of the agencies anaemic. A parliamentary inquiry was set up – which led to cross-party agreement that the law was outdated and increasingly irrelevant, and in turn to the overhaul of the Regulation of Investigatory Powers Act.

The initial reaction to the Paradise Papers has mirrored the early arguments around Snowden. Wealthy people who use offshore arrangements and the industries that support them have defended the status quo, and pushed back against reforms that would allow everyone else to see what’s really going on in British tax havens. “Where’s the wrongdoing?” they say.

Setting aside the fact that HMRC has already begun to review certain tax arrangements on the Isle of Man, it’s a question that seems as ridiculous now as it was in 2013. Because if there is one big lesson from the Paradise Papers, it’s that currently legal tax avoidance by certain companies and individuals has been shown to be as antisocial, immoral and unfair as many of the arrangements that are banned.

Theresa May refused to commit to a public register of the ownership of offshore companies and trusts

The laws that allow it have been shown to be open to exploitation, out of date, and in thorough need of urgent review – especially when set against the backdrop of 21st-century austerity, an austerity that we know, after Wednesday’s budget, will endure for years. And the authorities that are supposed to police all this are hopelessly outgunned.

The point was made by the Isle of Man’s chief constable, Gary Roberts. In May he described financial crime as a “genuinely strategic threat”. He said that the nature and scale of the investigations engaging his small force were “without precedent”. And he added: “If you are going to play in the big world of offshore finance, you’ve got to have the infrastructure to support it.”

From the Paradise Papers documents, it’s clear the police and the regulators don’t have that. The people who do are the accountants, lawyers and tax advisers who run legal rings around investigators, and conjure arrangements and schemes that allow their already wealthy clients to shelter more of their cash. You don’t have to be a chief constable to see there is something morally very wrong about this.

Yet the government’s reaction has been telling. Did ministers express fury at the idea that money it desperately needs to pay for public services is being spirited offshore? Were there promises to re-energise the Tories’ general election manifesto commitment to take “vigorous action against tax avoidance and evasion”? No, there were not. The prime minister was defensive, merely saying “work is already being done” without further explanation.

“We want people to pay tax that’s due,” Theresa May said, but she refused to commit to a public register of the ownership of offshore companies and trusts, which would at least offer greater transparency.

Then came the claim that the prime minister’s disinclination to do anything, or express anything, wasn’t her fault – it was the Guardian’s. At a lobby briefing, a Downing Street spokesman told reporters that HMRC couldn’t check for wrongdoing unless the Guardian and its partners handed over the leaked documents.

The Guardian published more than 50 stories from the Paradise Papers – within them are clues enough, you might have thought, for HMRC to start making its own inquiries, or for a cash-strapped government to express a degree of concern about the vast amounts of money leaking away from the Treasury.

So where does that leave us? This latest leak, like Snowden before it, has revealed an empire that has grown exponentially and in secret. It’s an empire that is poorly regulated and in desperate need of reform. And it is currently being protected by the state.

It took months for David Cameron’s government to concede that Snowden’s revelations couldn’t be ignored. It might take a few more before May learns this lesson from the past. Labour has called for a public inquiry – but at the very least the government, as it did after Snowden, should set up a parliamentary inquiry. It needs to find out whether our laws are fit for purpose, and whether the people who police them have the resources they need. Given the evidence so far, the answer to both questions would appear to be a resounding no.

• Nick Hopkins is the Guardian’s head of investigations