Murphys' voice: A draw in its own right

"There are a lot of opportunities out there for celebrities in animation and we're going to see this trend grow," Ms Stecher told the BBC.

Cameron Diaz, a newcomer to voiceover work, recently supplied the voice for Princess Fiona in the animated blockbuster Shrek.

"It was a great experience," she told the BBC.

"It took place over a couple of years - it's a process because you put the voice out and then they have to animate to the voice."

Shrek has been a huge hit, and it was recently reported that Diaz is now being paid �10m to reprise Princess Fiona's voice in a sequel.

Myers: one of the A-list Hollywood voices

Sums like that - which are exceptional - make doing voice-only roles an attractive prospect.

But some actors say they are drawn to the work because of the creative challenge.

Eddie Murphy, who did the voice for Donkey in Shrek, told the BBC: "I found the director and the people involved were really specific about what they want - they talk you through things.

"Then they draw how they want your voice to go - because he was a little more angry, or a little more scared - and you see that come out."

The big studios pay to have big-name stars in animated projects because they know their presence will sell their film.

David: Professionals "being relegated"

Shrek was undoubtedly helped on its way to blockbuster status because it came packaged with the brand-name familiarity of voices like Eddie Murphy and Mike Myers.

But the growing use of Hollywood A-list stars in cartoons has had an impact on professional voiceover artists.

Actor Keith David, who has done dozens of voice-only roles, most recently in the animated Final Fantasy, says that unless you are a big name star it is now quite hard to get plum voiceover roles.

"Certainly the guy who's making a very decent living doing lead voices in animation is now being relegated to featured voices, " Mr David told the BBC.

But right now, studios see the involvement of stars in animation as a winning formula - and for actors it is definitely becoming an art that is earning respect.

This year Eddie Murphy even earned a Bafta nomination for best supporting actor for playing Donkey in Shrek - a role in which he is very much heard and not seen.