Yorkshire peer Earl Peel, a leading hunt supporter, said the House of Lords' examination of the Bill showed it was unworkable and called on MPs to reflect on its enforceability.
He highlighted the fact that it suggested terrier work should be allowed for the protection of birds to be shot but remain illegal even where farmers are attempting to protect livestock or rare birds.
"It's an unworkable piece of legislation," said Earl Peel. "This Bill has got to be blown up.
"We've given it full scrutiny and torn it to pieces and found the anomalies are quite extraordinary.
"Good law has to be enforceable. This isn't."
Both Houses of Parliament are set on a collision course after Tuesday's vote by peers to allow regulation of the sport instead of the outright ban demanded by the Commons and a vote on Wednesday to back tests of "utility and least suffering" for registered hunts.
Lords will send the Bill with their amendments back to the Commons after November 16, where the Parliament Act to force it onto the statute book will now almost certainly be invoked by the Speaker if peers sticks to its guns. The impasse is likely to ensure that unless there is further manouvering in Parliament, foxhunting will be banned by February instead of the July 2006 date originally envisaged by Downing Street.
Earl Peel illustrated another complication with regards to shooting.
"If you have more than two dogs and flush out an animal you're committing an offence unless you shoot it," he said.
"Under this ridiculous piece of legislation you have to do that, to prove that you're out shooting rather than hunting with dogs."
Government Minister Lord Whitty has warned that the Lords' vote for the "constructive compromise" of a licensing scheme may now have come too late to save a total ban on hunting.
He said "coherent" proposals to allow hunting with hounds to continue under licence could not be enough to prevent the lower house using the Parliament Act to enforce its will.
Simon.McGee@ypn.co.uk