Grand National-winning jockey Jason Maguire has criticised the decision to change the Aintree course for 2012.
Three fences are going to be altered after a review of April's race in which two horses were fatally injured.
Maguire told BBC Radio 5 live: "From a jockey's point of view, we say no. We'd hate to lose the character of the race.
"If you lower the fences and make things a lot easier you're going to have horses going quicker and that might cause a problem."
Following this year's deaths the Aintree executive and British Horseracing Authority examined every race run over the fences since 1990 - when Becher's and Valentine's Brook were last re-modelled.
It was noticed in statistical analysis that the first, fourth and Becher's contributed to the greatest number of incidents - 21%, 12.6% and 21% respectively of all falls since 1990.
The fourth and Becher's, which is the sixth fence on the first circuit, were highlighted as being more difficult to jump than the others.
A decision was taken to again re-profile the landing side of Becher's, level the first and reduce the fourth by two inches, while increasing the height of all toe boards.
"It's a great spectacle for people watching, it's a got millions of viewers and they watch it for that reason [the spectacle] alone," said Maguire, who won on Ballabriggs.
"It [the horses' welfare] is crucial. It's very sad when horses do get fatal injuries but in every walk of this sport you're going to have deaths.
"When horses are involved you're going to have fatal injuries, even racing just during the week with normal park horses you'll have fatal injuries. It comes in every walk of life.
"The way it is at the minute, the fences are big and you have to have horses back on their hocks to actually go and jump the fences - and jockeys aren't in such a hurry because they realise the horses have to jump off their hocks.
"If you make the fences lower people might end up going quick and that could be a problem."
The fences will have been changed in time for this December's meeting.