A Labour government may be forced to raise taxes on the wealthiest in Britain to reduce national debt, according to economists. Sir Keir Starmer has repeatedly promised not to increase two-thirds of the tax base including income tax, national insurance, corporation tax or VAT. However, a weak growth outlook makes the Labour manifesto promise to stabilise debt look unmanageable unless they look across the tax base, according to experts. Economists have said the strategy might win it more support but it significantly reduces the party’s options for dealing with the fiscal challenge that awaits i…