What is going on with Vince Cable? While reviews of his foxtrot on Strictly Come Dancing were positive, all else seems to be going awry – from university tuition fees to the statements he let slip about Rupert Murdoch.

Twelve days ago we brought a question of human rights to his attention where he could score some rebound points. Yet, though it is an urgent matter of life and death, his office seems unable even to sort his post.

The issue involves a new twist in the export of British lethal injection drugs to the United States. Going back two months, when Reprieve first learned that Jeffrey Landrigan was to be executed with British drugs on 26 October, we felt sure that Cable would act decisively: after all, he is vigorously opposed to capital punishment. But he did not impose an export ban for 30 days, until we forced his hand in the high court. Then, on 6 December, we learned that California was trying to import enough British sodium thiopental for 85 executions. Cable did nothing, again appearing resolutely irresolute.

Most recently, on 16 December, we discovered that Arizona was importing all three of its execution drugs – not only sodium thiopental, but also pancuronium bromide and potassium chloride – from British sources. We asked Cable to issue an urgent export ban by the following Monday. Still we received no reply.

This morning, the Today programme ran a story on the British execution drug export bonanza. The BBC asked Cable's office what he planned to do about it. Imagine my surprise at the response.

"We have seen media reports speculating on the sources of the California state's supply of potassium chloride and pancuronium bromide for use in lethal injections," Cable's spokesperson told BBC Radio 4. "Currently there has been no formal request received by the Department to control the export of these drugs. Any such request will be carefully considered and will assess the likely effectiveness of any export control against the impact on legitimate trade."

In other words, Cable denies ever being asked to ban the drugs. What is up with the Department for Business, Innovation and Skills? I hate to accuse anyone of dissembling, but the alternative is perhaps worse: Cable's office seems to lack the ability to read their post.

In light of his previous inertia, we took ridiculous precautions to ensure that Cable got the message 12 days ago: we sent him the "formal request" for a ban simultaneously by email (I sent it personally at 39 seconds after 10.35am on 16 December), by fax (the verification sheet reflects that it went through at 12.15pm), by hand (delivered by a colleague) and by Royal Mail.

Indeed, two days ago, I sent another request, giving him until close of business on Friday to impose such a ban, or face potential litigation. We have not received even the courtesy of a one-sentence reply.

It is admirable that Cable spent 20-odd hours refining his dancing skills over these 12 days of Christmas; but, as the strains of Winter Wonderland fade away, he might spare a few minutes for the lives of these condemned prisoners.

I have been saddened to witness Cable's recent travails. He built a reputation as an amiable chap who was willing to stand by his principles, and speak unpopular truths. But reputations are, as my grandmother used to say, hard won and easily lost.