At first reading, it sounds like a classic political morality tale: an idealistic new prime minister, just before a difficult upper house election, discusses openly the need for a higher consumption tax. Voters duly deal his party a crushing defeat. The moral of the story: only a fool thinks honesty is the best pre-election tax policy.

Such a cynical interpretation of the upper house election setback suffered by Japan's Democratic party last weekend seems to chime with recent events in the UK. There, the new Conservative-Liberal Democrat coalition lost no time unveiling an increase in value added tax to 20 per cent, despite both parties having disavowed any such plan during their campaigns.

Naoto Kan, Japan's prime minister, knows well the dangers of consumption tax talk. The levy has been political poison in Japan since its reintroduction was first discussed in the late 1970s, and attempts to raise the rate have contributed to the downfall of at least two prime ministers since 1993. But tax was hardly the only factor in a DPJ defeat that some think may result in Mr Kan becoming the fifth prime minister in a row to last a year or less in office.