MPs have voted down a new clause to put protections for animal sentience into Brexit legislation, despite fears the Government's plans will not come into effect quickly enough.
Green MP Caroline Lucas urged ministers that her "belt and braces" approach would provide legislative certainty as she warned MPs that plans from Environment Secretary Michael Gove may not be on the statute book before Britain leaves the bloc.
However, the new clause was defeated by 320 votes to 297 - majority 23.
Ms Lucas was reiterating calls she made at a previous stage of the European Union (Withdrawal) Bill, which would have transferred an EU protocol recognising animals as sentient beings into domestic law.
The vote against her amendment prompted a social media backlash while Mr Gove has since tabled a draft Bill enshrining animal sentience into UK law post-Brexit and introducing jail sentences of up to five years for animal abusers.
Speaking at the Bill's report stage, Ms Lucas said: "The new laws on sentencing are certainly to be welcomed but I don't see why we have to have an either/or.
"What I am simply trying to do is to make sure that there isn't a legislative gap, because I don't have confidence - maybe those on the other side do - but I don't have confidence that this new Bill, brought forward by the Secretary of State, is likely to be on the statute books by the time we leave the EU, if that's what happens.
"I simply want to make sure that there is legislative certainty, belt and braces, by making sure that we have my amendment in that EU Bill as well."
Solicitor General Robert Buckland, responding to the debate for the Government, said the Government intends to "enhance" animal welfare standards after Brexit.
He said: "It ill-beholds (Ms Lucas) to assume that this party somehow lies on a lower moral plane when it comes to issues of animal welfare.
"We share the passion and commitment to animal welfare that she professes."
He added: "We want to hear the public and their view about it, and we want to get it right in domestic legislation, which is the right place for it."