The government has promised to ban the use of wild animals in travelling circuses "at the earliest opportunity".
Animal welfare minister Lord Taylor described the use of creatures such as tigers, monkeys and zebras in performances as "outdated".
He added that a tougher licensing system would be implemented until the ban is in place.
Between 35 and 50 wild animals are believed to be working in circuses. MPs backed a ban last year.
Although the Commons vote was non-binding, the government later said it would act on the decision.
But it warned that it could be left open to lawsuits from circus owners and workers.
That is a hurdle that is still likely to make progress of the ban slow.
'Serious legal issues'
In a written parliamentary statement, Lord Taylor said: "There is no place in today's society for wild animals being used for our entertainment in travelling circuses. Wild animals deserve our respect.
"We have said many times we wanted to ban this outdated practice, but before we could do that there were serious legal issues we had to consider.
"We are developing proposals to introduce a bill as soon as parliamentary time allows.
"In the meantime we are introducing a Circus Licensing Scheme to ensure decent conditions for wild animals in travelling circuses."
In the Commons, environment minister Jim Paice was pressed by MPs on the timing of the ban, but replied: "It's impossible to put an exact date on it but I would be extremely surprised and disappointed if it's not implemented before the next election."
For Labour, shadow environment minister Fiona O'Donnell said: "Last year Parliament voted unanimously to ban wild animals from circuses with the backing of 95% of the public.
"Defra ministers showed how out of touch they are with the public and hid behind spurious threats of legal challenges in the EU as an excuse for doing nothing.
"Now they are saying they will introduce a bill when parliamentary time allows. But yesterday, they introduced a water bill which will be passed in just two days. Why can't they do the same with this?"
The calls for a ban increased following revelations of the mistreatment of a circus elephant, Anne, last year.
A consultation on welfare licences has been launched and the regulations are expected to come into force by the summer.
Anyone responsible for a travelling circus that uses wild animals in a performance will need to hold a valid licence, meet welfare standards and have a retirement plan for each animal.
They will also need to provide proper accommodation, full veterinary care, a good diet and high welfare standards during training and performances.
A government-appointed inspector, paid for by the circuses, will ensure rules are met, officials said.