It's gone! Yesterday in parliament John Healey confirmed that tax will be imposed on red diesel for leisure use:

Mr. Alistair Carmichael (Orkney and Shetland) (LD): What recent progress has been made in negotiations to extend the derogation from EU regulations to enable UK pleasure boats to use red diesel in 2007; and if he will make a statement. [104886]

The Financial Secretary to the Treasury (John Healey): I know that the derogation that permits the use of red diesel in Britain is highly valued by private boat owners and users. Thirty-four separate derogations from the directive are held by member states. None has yet been approved by the Commission and 14 have been rejected so far. Late yesterday afternoon, it was confirmed to me that the Commission had decided not to renew the UK’s application for a fresh derogation for private boats. I know that will be unwelcome news. As we have argued to the Commission, it could be highly complex and costly to implement the measure, so today I asked officials to meet concerned and affected organisations soon to discuss the implications of the Commission’s decision.