I was dismayed to read in Mohsin Khan’s recent piece calling for an NHS contribution that the leadership is, again, considering an NHS tax.

How history repeats itself. Ten or so years ago, when working for the Welsh Party, I opposed plans for what the Federal Policy Committee was then also referring to as an NHS contribution. My contention was, and remains, that a commitment to a Federal UK is not compatible with hypothecated taxation.

Whilst taxes are collected at a UK level, spending priorities are determined by devolved institutions. In our devolved context, any claim that a tax is truly hypothecated is simply dishonest. We could not guarantee that a centrally collected NHS tax would be spent on the NHS in Wales, Scotland or Northern Ireland.  It is impossible to require a particular portion of taxation to be spent in the devolved nations on specific areas without requiring them to do so by law.  This would laugh in the face of the liberal principle of subsidiarity and is clearly a non-starter.

If this is the case, could a hypothecated NHS tax be applied in England only? Not in my view. Even if you set aside the logistical nightmare of collecting differing taxes in different parts of the UK, it would do nothing to address the significant health inequalities between England and the rest of the UK. If anything, it would widen the gap.

Prior to devolution, we got away with it. Who can forget our penny on income tax for education?

It was our flagship policy in the 1997 election. It was a simple and populist policy that we were clearly identified with, an electioneering dream, you might say.

Hypothecation has had its day. We cannot let the pursuit of eye-catching policies get in the way of constitutional reality. The UK has moved on since 1997, and so must we.

* Energlyn Churchill is a pseudonym. He is a Welsh Liberal Democrat. He is active in his local party and serves on a Welsh Party committee. He blogs at Towards Gunfire.