Disability rights campaigners have criticised Chester Zoo for introducing a policy of charging carers.
The zoo, which attracts 1.3 million visitors a year, decided to start charging carers accompanying disabled people two years ago.
The Muscular Dystrophy Campaign's Trailblazers group said the decision charges people for their independence.
Chester Zoo said that after consulting other attractions it "felt that was the right thing to do".
"We have come into line with other attractions"
Said Chester Zoo's head of marketing, Martin Clancy
Carers and disabled people are charged the concessionary rate of £15.25 for entry in high season - a discount of £1.65 on the full-priced ticket.
Catherine Alexander, 19, from Thingwall, Wirral, who has muscular dystrophy and is a member of its Trailblazers campaign group said: "I don't see why I should have to pay for someone to come with me when there's no way I would be able to go by myself. This is not my choice."
"They never used to charge for carers but when I went recently I had to pay for myself and and a carer which is unacceptable.
"I didn't used to have a carer to come with me, but it's now more a necessity than anything," said Miss Alexander, a student at Lancaster University who now requires 24-hour carers to help her live with her progressive disability.
Chester Zoo's head of marketing, Martin Clancy, said that the charge was introduced in 2008 following consultation with other UK zoos and attractions.
"We have come into line with other attractions. After carrying out consultation we felt that this was the right thing to do."
He added that groups of disabled people and carers could use the zoo's group discount scheme.
Trailblazers spokesman Bobby Ancil said: "Charging for carers is is making disabled people pay for their independence."
He said visitor attractions should follow the example of the Cinema Exhibitor's Association, which has produced a card to allow carers free admission to cinemas.