I HAVE never been comfortable with the idea of retrospective legislation. If Parliament is going to change the rules, people should normally be able to rely on the law of that moment. That principle matters, with some notable exceptions such as anti-forestalling measures in tax law designed to prevent people gaming the system, as with Capital Gains Tax changes in 2024. Yet some of what has been said in recent days about political donations risks generating more heat than light.

The argument now being advanced by recent turquoise benefactors – and one often presented dangerously selectively – is that applying new donation limits would amount to unfair retrospective punishment. Genuine retrospective punishment should raise eyebrows, but I am not convinced the issue is quite so straightforward.

For a start, much of Reform's morally questionable £72-million in crypto funding has not yet been dispersed because of the way the donations have been structured. There is an obvious distinction between trying to recover funds already spent and applying new rules to money that has yet to enter the political system.

This debate also did not appear overnight because of the latest mega-donations. Steve Reed set out plans for donation caps months earlier, with the proposal applying from the date of announcement to prevent a rush of contributions before legislation took effect. Both the timetable and the principle were already established long before these latest sums became front-page news.

There is also a practical question facing any government. Announce a future change in the rules and people often rush to act before it takes effect. The government has already recognised the same risk in relation to foreign financial interference in British politics: reforms can be undermined if advance notice creates a window for people to sidestep their intended effect.

Reasonable people can disagree about where the balance should be struck. What they should not do is pretend this debate emerged solely because of recent donations. Christopher Harborne was already under investigation before these donations became front-page news, while Dmitry Leus Delo has previously been convicted of moneylaundering-related offences and has financed a controversial libel claim defending alleged antisemitism. Whatever legal conclusions ultimately follow, the rightful scrutiny did not arise in a vacuum.

More broadly, the direction of travel should concern all of us. Across the country, there has already been a noticeable increase in negative campaigning, with hostile leaflets landing on doormats and AI-generated content presented as independent analysis. Much of it is dressed up as impartial research despite being paid-for political messaging. Voters deserve greater transparency about who is financing campaigns seeking to influence them.

Reform UK has reportedly received more in donations than all political parties spent during the 2024 General Election campaign combined. With the spending cap for a single party at just over £33-million, those funds could effectively finance two full national campaigns.

The question facing Parliament is whether our political system remains an arena for ideas or becomes an ever-expanding auction house where money increasingly determines who gets heard. That is a debate we need to have properly, and without caricature from anyone.