Last week Vote Leave, the Brexit campaign group headed by Boris Johnson and Michael Gove, was fined £61,000 and referred to the police by the Electoral Commission for breaking electoral law by funnelling more than half a million pounds to the pro-Brexit youth group BeLeave.

We should all see this for what it is: an affront to democracy, regardless of which side of the Brexit referendum we were on. Both Leavers and Remainers agree electoral campaigns must respect the law if we are to have a functioning democracy.

These infringements by Vote Leave are also an affront to the public’s trust in politicians in general and in this government specifically. Not only was this campaign fronted by Boris Johnson and Michael Gove; many other senior Tory MPs were involved in it – the transport secretary Chris Grayling, the international trade secretary Liam Fox, and the new Brexit secretary Dominic Raab were members of the campaign committee, as well as Iain Duncan Smith and Priti Patel. They must now cooperate fully with the police investigation and take all necessary steps to restore public trust.

During Prime Minister’s Questions last week Theresa May was quite flustered when Jeremy Corbyn asked her to guarantee her cabinet ministers would cooperate fully with the investigation. This Tory government must come clean: who knew what and when? And what will the consequences be?

It is Theresa May’s duty as prime minister to defend our democracy, even if and especially when that means calling to account her own ministers and backbenchers.