People who enjoy non-domiciled tax status in the UK will be required under the next Conservative government to pay an annual Offshore Domicile Levy of £25,000.
Plans for the flat charge were announced by the shadow chancellor, George Osborne, during a keynote speech at his party's annual conference in Blackpool.
The intention of the proposed levy will be to safeguard the country's attractiveness as a place for wealthy foreigners to live, because their tax status will be guaranteed.
Mr Osborne told delegates that it is a 'good thing' that the UK has 'a number of people… who register for non-domiciled tax status offshore. It is a good thing for Britain that they live here and bring their talent and their investment to our economy'.
He went on to promise not to 'tax all that income as Gordon Brown has persistently threatened to do'. However, in return for the shadow chancellor's pledge, the Conservatives will 'charge a flat annual levy of around £25,000 for those who register for non-domiciled status'.
This, he said, would be 'easy to administer, difficult to avoid' - and it 'strikes the right balance between a fair tax system and a competitive economy'.
The Tories estimate that 150,000 UK residents of foreign origin domiciled offshore would pay the proposed charge, meaning £3.5 billion would be raised annually.
According to Mr Osborne, the funds would pay for plans, also announced at his party's conference, to raise inheritance tax threshold to £1 million and abolish stamp duty homes worth less than £250,000 purchased by first-time buyers.