Switzerland could scrap tax breaks for foreign millionaires after activists succeeded in getting a more-than-century-old law put to a popular vote.

At present wealthy foreigners living in the Alpine tax haven are only required to pay a flat fee instead of income tax.

Four of Switzerland’s 26 cantons have already binned the rules, which are a source of resentment among ordinary Swiss who pay more tax than wealthy expats.

More than 5,000 foreigners, including many senior financiers, use the rules to minimise their tax