New laws to ban or restrict fox-hunting should not come into force until the end of 2007, says the House of Lords.
A ban on hunting is once more on the cards
Peers on Thursday voted to delay any limits on hunting with dogs until vets reported on whether it caused more pain than other pest control.
It puts the Lords on another collision course with MPs. Peers have already replaced plans for an outright hunting ban with a licensing scheme.
But a complete hunt ban is set to be pushed through Parliament next week.
MPs had already agreed to allow any ban to be delayed until July 2006.
That proposal has yet to be put to the Lords. Environment Minister Lord Whitty said the government was waiting to see the ultimate shape of the Bill.
But on Thursday, peers voted to allow unrestricted hunting to continue until the end of November 2007.
Any restrictions after then could only come into force if the government had received a report from the Royal College of Veterinary Surgeons on "the relative pain, suffering or distress caused to wild mammals by hunting with dogs compared with other methods of controlling those with wild mammals", they said.
It would then be up to the environment secretary, rather than Parliament, to decide whether to implement the Bill.
In a separate vote, peers also voted down a compromise which would have banned stag hunting but allowed other hunts to continue.
The Bill is set to have its third reading in the Lords on Monday and return to the Commons on Tuesday.
MPs are expected to overturn the Lords' amendments and insist on an outright ban on hunting with dogs.
The Bill then returns to the Lords on Wednesday for debate on amendments.
Deputy Commons Leader Phil Woolas has said he is confident there is enough time to debate the plans before the current session of Parliament ends on Thursday.
The government has already said it would use the Parliament Act to push through the Bill if peers try to override MPs wishes.
Responding to questions about what the procedure would be, Mr Woolas said it would be a matter for the House, but the Parliament Act was "more of a process than a decision".
Labour MPs would be given a free vote on the issue, he added.
If the parliamentary session ends without agreement, the Bill effectively becomes law automatically.
Ministers do not need to take any specific measures to invoke the Parliament Act.