Osborne’s letter follows news of Henderson Group, Regus and Charter’s plans to leave the UK tax domain and calls on Darling to adopt the Conservative’s plans to cut corporation tax.
The latest companies to announce offshore plans join United Business Media and Shire Pharmaceuticals, who have already said they are relocating to Ireland.
In his letter Osborne writes: “It is further evidence of the damage done to the UK by the confusion you have caused in the last year over the future of our business tax regime, combined with the fact that ten years of a Labour Government has left us with some of the highest corporate tax rates in the European Union.”
He adds: “As you demonstrated in last year’s Pre-Budget Report, you are capable of adopting Conservative proposals.
“With companies leaving Britain, weakening an already ailing British economy, I urge you to adopt our proposals in order to restore our competitiveness and help prevent any more companies from deciding to leave the UK.”
The Conservatives propose reducing the main corporation tax rate from 28 per cent to 25 per cent, which it says could be funded by simplifying capital allowances.