Peers set to vote to block chlorinated chicken imports after Brexit

However, critics – including several Tory rebels – fear that the new legislation could ultimately erode standards and lead to the importation of chlorinated chicken.

The PM is facing a Tory rebellion on the issue over an amendment already passed by peers to beef up the Agriculture Commission, which would make it harder for the government to renege on standards.

The government insists it will not water down standards but sources believe there are around 30 Tories who could rebel in the vote on the agriculture bill, which could come as early as next week, because the rebels want tougher protections written and put into law.

The Labour source told HuffPost that the Lords expressed confidence that peers would again vote to either block imports that do not meet existing British standards or toughen up parliamentary approval of trade deals.

The source cautioned the government against seeking to delay either bill, warning that “they can only kick the can so far down the road and will need to deal with the widening concerns of their own MPs at some point”.

Tory MP Neil Parish is a leading rebel and has urged the government to back the plans to strengthen the Agriculture Commission,  saying he has “serious concerns” about maintaining standards.

Parish chairs the Commons environment, food and rural affairs committee and said: “With the agriculture and trade bill being amended in the Lords, parliament clearly has serious concerns about legislative protections and scrutiny when it comes to trade deals. 

“The government has said it wants to maintain our standards, but let’s have a proper system in legislation to scrutinise those standards when trade deals are proposed. 

“The EU and USA have those protections. 

“If we’re taking back control of trade policy, let’s have the gold-standard”.

Lord Stevenson of Balmacara, Labour’s shadow trade minister has backed Parish’s calls to give parliament a say over trade deals and to maintain standards.

He said: “The government seems determined to keep using the archaic royal prerogative to approve trade deals, so that parliament has no role – despite the impact these decisions have on food and environmental standards. 

“It’s hard to see what benefit we get from allowing chlorinated chicken and hormone-injected beef to flood into Britain from the US. And our hardworking farmers and consumers will lose out.

“Labour’s amendments, which have widespread support across the Lords, aim to protect our food standards and safeguard the environment, and give parliament a proper say over future trade agreements.”

The PM’s official spokesperson was asked on Wednesday if the government would accept the Agriculture Commission proposal in the face of a Tory rebellion.

The spokesperson replied: “We have said right from the outset that we will not compromise on our high food standards in all of our trade negotiations.

“And it is illegal in UK law – you can’t import chlorine washed chicken and hormone-fed beef, that’s been retained as part of the EU Withdrawal Act.

“In terms of the specific amendment, it’s not a discussion which I have had.”