Theresa May and Arlene Foster. Image, BBC.

Tomorrow afternoon the House of Commons will be asked to legitimise a con trick, a crass act of political and financial dishonesty, by passing a flawed law that does the very opposite of its title.

If the government, as is likely, wins and delivers cynically time-limited new rules on the “Transparency” of donations and loans in Northern Ireland it will have succeeded, for now, in hiding the original source of £435,000 that was channelled through the Democratic Unionist Party for its Leave campaign in the EU referendum.

The money was spent mostly on the UK mainland on campaigning to take the UK out of the EU. It passed through the hands of a secretive organisation in Glasgow, the Constitutional Research Council. But where exactly did the money come from? Right-leaning groups in the United States wanting to see a populist rising in Britain they could subsequently build on at home? Russia, who now see state-sponsored interference as an attractive tool of disruption? Or perhaps a UK-based group who wanted to keep their political influence private? We don’t know. And it’s likely that the Electoral Commission doesn’t know everything either. But there are things they do know. And they want to tell us – but the government is gagging them.

Regardless, this lack of transparency only builds mistrust and dissent. If our politics is dark and our governments believe they can manufacture financial secrecy without accountability, we are risking the foundations of our democracy.

Should the government win, ministers are likely to indulge in a faux celebration, declaring a new era of openness in Northern Ireland political funding. It will be a lie. They will, in reality, have deliberately circumvented the right for us to know what interests this minority government and the small party that props it up, may be answerable to beyond those it supposedly represents.

This is why openDemocracy has spent months investigating the sources, processes and pathways that led to the DUP receiving almost half a million pounds and how the money was subsequently used. We have tried, and partially succeeded, in breaking through the barriers that protect where the money came from, and explored the wider institutional unease which still surrounds this cash.

The watchdog authority, the Electoral Commission, responsible for upholding the law, want to give the public the details of their own investigation into this money. They have pointed out that the government already has the power to simply back-date the new transparency rules to 2014 and therefore allow the publication of all the information held on the DUP funding.

The former Northern Ireland Secretary, James Brokenshire, announced last year that the political climate in Northern Ireland had changed significantly and that an era of “full” – his word and one not difficult to define – transparency should begin.

Yet the government’s gift to this landmark of openness is instead a reflex protection of itself and its DUP partners, limiting “transparency” to include only the period since July last year. This legally seals all information about political donation from the past two general elections, two Assembly elections, the EU referendum and the period covering the Renewable Heat Incentive scandal.

When we most need faith in politics, this debacle has instead given us the elements of a fraudulent pantomime. Tomorrow in the Commons, MPs are being asked to authorise the building of a large wall and vault around a sum of money that clearly holds a significance beyond mere currency. Truth, as they say, never damages a cause that is just. So, what exactly is the government and its DUP allies determined to hide? Why are they installing legal barriers that will block those trying to throw light on this dark corner of Northern Irish and UK political finances? In other words, what are they determined to prevent the electorate, those who put them in power, from knowing?

This intense circus of secrecy, this deception, this con, can begin to end tomorrow afternoon. MPs, all of them, should ask why their constituencies put them there. The stark answer is we have a representative democracy and at its core is accountability – and there is no accountability if the public are denied the right to know who funds and is hiding behind our political decision-making.

The House of Commons should throw out this law and demand the “full” transparency the people of Northern Ireland are entitled to. And if the DUP are serious about wanting to be treated the same as the rest of the UK, they and their “dark money” should not be allowed to hide behind a wall they helped Theresa May’s government to build.