There are three reasons why the UK government has yet to show itself to be serious about sanctions against figures linked to Vladimir Putin’s regime in Russia.

Together, they show the threat the UK poses to the effectiveness of the international response to the invasion of Ukraine. They also reflect the UK’s deep vulnerability to corruption, and the extent to which the UK continues to facilitate corruption and tax abuse all around the world.

The UK government has participated, thus far, in the international response to Russia’s invasion. It is a signatory with the EU and US to last week’s joint statement on “further restrictive measures” that may herald one of the most far-reaching steps to pierce financial secrecy.

But Britain’s own action on oligarchs has been criticised by Labour, and by Tory backbenchers, as paltry by comparison with those of its allies. While the EU has now blacklisted a clutch of billionaires, including Russia’s richest man, Alexei Mordashov, Boris Johnson’s government has been timid. The most significant new name on the UK list is Alisher Usmanov, added on Thursday night, in an announcement rushed out minutes before President Joe Biden revealed the US would join the EU in blacklisting the metals tycoon.

The first reason for this lack of ambition may be the simplest. The Conservative party has long received funding from figures connected to – or at the absolute minimum, rich after association with – the Putin regime. Political donations may or may not lead to direct influence. With certainty, however, and much like the ownership of leading football clubs, they raise profile and a sense of being part of the establishment.

The second reason is closely related, and more substantive. Being part of the establishment reduces the sorts of difficult questions that may be asked – for example, over the source of your money, or your appropriateness as a client for professional services firms, or whether your company should be allowed to raise funds on an international stock market like London.

Russian business interests are embedded in the City of London. Lobby group TheCityUK played a central role in establishing the Moscow International Financial Centre, with successive London lord mayors co-chairing the “Joint Liaison Group”. London was until this week a huge market for trading in the shares of Russian companies. All of this has created strong financial incentives to limit the extent of any sanctions.

The third reason for the UK dragging its heels is the deepest, and again entirely related. Together with its Overseas Territories like Cayman and its Crown Dependencies like Jersey, the UK is the biggest actor globally in the provision of financial secrecy services – leading to an estimated tax loss worldwide of some $190bn annually. And there is still, in certain circles, a Brexit vision of the UK as the big tax haven between the EU and the US (less Singapore-on-Thames, more Caymans on steroids).

Leading the charge on effective sanctions against Russian money would threaten that vision. So too would a meaningful outcome for the transatlantic taskforce, proposed in Saturday’s joint statement on sanctions against Russia, that is intended to clamp down on anonymous assets. Other measures are needed. The Tax Justice Network has now laid out 10 key steps that the taskforce could pursue to introduce and tighten up the reporting and verification of beneficial ownership, culminating in a global asset registry that could end anonymous wealth once and for all.

A UK that joins the fight against illicit finance is a UK that finally closes the door on its tax haven empire. But for each of the three reasons above, it’s hard to imagine that the current UK government will commit to this.

• Alex Cobham is chief executive of the Tax Justice Network