Of the three indices - the all new construction index, the average earnings index and the corporate services index - the all new index increased by 46%, while the other two saw just 27%.

These increases gave a composite index equal to 5.1% and, as BW is committed to an efficiency saving for its customers of 0.5% pa until 2007, so the price of its licences will increase by 4.6% from April 2006.

"While it is disappointing to note the effect that the all new construction index has had on next year's price increase, we still believe that our boat licences offer terrific value for money when you consider the access they allow to the UK's 2,000 miles of canals and rivers, " said Sally Ash, head of boating development. "For the average boater, it amounts to about £7 per day spent cruising."

The main reason for the big jump in the construction price index, she added, was the unprecedented rise in steel prices.

The Gold Licence, administered by BW on behalf of the Environment Agency (EA), which allows boat owners to travel on both navigation authorities' waters, will increase by 5.2% with effect from January 1, 2006.

BW and the EA agreed to increase the Gold Licence annual fee by a weighted average of each navigation authority's own licence fee increase.

The weighting factor was proportional to the Gold Licences sold by each navigation authority to its own customers, which during 2005 was split 75:25 in favour of BW.