Lord Mandelson, the business secretary, was embroiled in a war of words with Britain’s biggest union on Thursday over the effectiveness of his efforts to protect Vauxhall’s 5,500 UK workers.

The fate of those employees hangs on what Lord Mandelson termed “very complicated” inter-governmental and corporate negotiations that will run on for several weeks. The outcome will help to shape future British industrial policy and could have significant political repercussions.