Increase in air passenger duty takes effect today

The increase in air passenger duty came into force today. There is an absurd position (discussed here) whereby even passengers who had pre-booked flights before the increase was announced were forced to pay the extra tax at the airport before being allowed onto their flights. However, some airlines (notably British Airways) graciously absorbed the increase, and did not pass it on to any passengers who had pre-booked with them before the date of the announcement.

Amid all this is the question whether this increase is even legal. The Chancellor of the Exchequer has no right to raise or increase taxes without the approval of Parliament. Parliament will not be in a position to approve this increase for a few months yet. The effect of this is that when they get round to doing so, the increase will be given retrospective effect. Is this legal? A lawyer argues in The Times today that it is not. If so, passengers are entitled to refuse to pay. Not just those who had pre-booked before the date of announcement, but any passenger intending to travel at any time before Parliament approves the increase.