Budget 2012: stamp duty rises to seven per cent on mansions "I regard tax evasion and - indeed - aggressive tax avoidance - as morally repugnant," Mr Osborne said. Together, the measures will affect thousands of the wealthiest property owners in the country and potentially push down the prices of valuable properties near the £2 million mark. Adam Challis, Head of Research at Hamptons International, said the stamp duty increase would potentially devalue around 2,600 homes, with about 400 properties now likely to be marketed below the £2 million mark. "Increasing stamp duty on properties priced at more than £2m will have a negative impact on transactions at the top end of the market and will disproportionately impact the London property market," he said. London's economy relies on being an attractive place for corporate executives to base their businesses. The Robin Hood Addiction can't go on forever without impacting London's global competitiveness. David Kilshaw, tax partner at KPMG, said the biggest blow to those with properties registered overseas would be the fact that savings on inheritance tax would be lower. "Most overseas nationals bought their UK property via a company not to save the relatively modest stamp duty but to avoid inheritance tax," he said. Whereas stamp duty would be £1 million on a £20 million home, that paled into insignificance when compared to the 40% inheritance charge which would be £8 million on death. Mr Kilshaw said many wealthy foreigners would now be likely to look elsewhere when they want to buy a big property. "Inheritance tax will now stalk the streets of Chelsea," he said. This could change the whole dynamics of the London property scene. Overseas investors may now think twice before they buy in London . For overseas nationals, this is a mansion tax with a capital M.