US president George Bush has decided to impose tariffs of up to 30 per cent on steel imports, ignoring Tony Blair's personal plea not to go ahead with the protectionist measures.

The move has angered the British government and brought threats of retaliation from EU trade commissioner Pascal Lamy, who is also set to lodge a complaint with the World Trade Organisation.

Trade and industry secretary Patricia Hewitt called the decision "wholly unjustified", while steel makers fear it could cost Europe four million tonnes of exports and thousands of jobs.

The imposition of the tariffs has renewed speculation over the letter sent by Blair to the Romanian government in support of Lakshmi Mittal's bid for its steel industry, as the Labour donor had called on Bush to make this move.