Britain is prepared to permit imports of chlorinated chicken from the US but will slap high tariffs on cheaply-produced food in order to minimise the impact on British farmers.

The latest Government proposal for a trade deal with the US is for a "dual tariff" regime that imposes different levels of duty on imported foods, depending on whether they comply with UK animal welfare standards.

Hormone-fed beef, chlorinated chicken and other foods that use techniques banned in Britain will be allowed across the Atlantic, but ministers want to use tariffs to make it uneconomical for US producers to export them to the UK.