Former Labourenvironment minister Jim Fitzpatrick said the government could easily achieve a ban using the existing Animal Welfare Act 2006, while Green MP Caroline Lucas said the government's judgment on the matter "is woefully lacking" and called for an end to the "cruel practice".
But a sizeable minority of Republicans are protectionist, and most Democrats insist that further liberalisation must raise labour and environment standards too.
Labour shadow environment secretary Mary Creagh said the only reason the extra testing was finally introduced was because of the discovery of horsemeat in beef products.