The Business Secretary, Vince Cable, said he was in favour of companies paying more than the minimum wage if they could afford it. But if wages are too high, it could lead to "significant loss of employment".
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Five people were killed and dozens more were injured after a car and knife attack in the capital on Wednesday afternoon.
Among those expected to attend the ceremony will be former US President Bill Clinton and ex-Northern Ireland first minister Peter Robinson.
Five people have been killed and 40 injured after a car and knife attack in London on Wednesday.