The Chancellor has warned businesses will face an increase in employer National Insurance contributions prompting accusations Labour is about to break a manifesto promise. Rachel Reeves said Labour’s election pledge not to increase National Insurance on “working people” related to employees, as opposed to the sum paid by employers. The Chancellor used the government’s international investment summit at London’s Guildhall on Monday to warn of tax rises to come in the upcoming October Budget. She refused to rule out plans to increase employer national insurance, insisting that businesses would u…