Britain on Wednesday extended a package of tariffs and quotas on five steel products by two years to protect local steelmakers, in a move that will breach international trade rules.
Trade minister Anne-Marie Trevelyan told parliament the safeguards would help defend a strategic industry and that British steel producers could face "serious injury" were the measures not maintained.
Britain's decision comes as the world's fifth-biggest economy charts its own trade policy since leaving the European Union in a strategy that has also included talks with a host of countries for bilateral free trade agreements.
"The decision ... departs from our international legal obligations under the relevant WTO agreement," Trevelyan added, referring to the World Trade Organisation.
"However, from time to time, issues may arise where the national interest requires action to be taken."
Trevelyan described herself as a champion of free trade but said the current circumstances warranted the extension of safeguards.
Britain is ready to take up any concerns raised by WTO members following its decision, Trevelyan added.