Eavis holds the festival on his farm in Somerset

His daughter Emily, who has helped her father to run the event for the last eight years, cast doubt over the future of the event in an interview.

"I... feel we should ply everything into this as if it be the last," she told the Orange World news service.

But Mr Eavis said the expression "treat it as if it is the last" was a family phrase and was taken out of context.

When asked by an interviewer if Glastonbury had a limited shelf-life, Ms Eavis said: "Yeah... it's a risky, risky business and it would be nice to think, to know that it could go on forever. But I don't know if that's possible."

'Middle-aged'

This year's festival will be headlined by US rapper Jay-Z.

KEY GLASTONBURY FACTS 1970 - First festival held 1978 - Glastonbury returned after a seven-year gap 1994 - The Pyramid Stage burnt down 2002 - The "ring-of-steel" fence was introduced 2005 - Two months' worth of rain fell over revellers in several hours, swamping the site 2007 - Ticket registration was introduced Source: Festival website

Mr Eavis said Glastonbury had become too "middle-aged" and he wanted to attract younger people this year.

Registration opened earlier this month.

It does not guarantee a ticket, but everyone who wants to buy a ticket when they go on sale on 6 April must have registered first.

Some 175,000 people will attend the festival from 27 to 29 June.