A war of words has escalated between Emmanuel Macron and Francois Hollande after the French president's predecessor warned that cutting back on the country's wealth tax risked favouring the rich "while they sleep" over the poor.
Mr Hollande's outburst was clearly timed to inflict maximum damage on Mr Macron, who is fighting a rearguard action to counter rival claims that he is "president of the rich"; it coincided with Tuesday's parliamentary debate on watering down the deeply symbolic "tax on fortune", which previous French leaders have dared not touch.
In an interview on Sunday, Mr Macron, who wants to limit the tax to property, railed against "French jealousy that seeks to tax success", saying it was pointless "throwing stones at the lead mountaineers" as if they fall, then they will bring down "rest of the roped party with them".
In an implicit broadside at his erstwhile protege, Mr Hollande - who famously once declared "I don't like the rich" - slammed what he called his attempts to introduce a "lower tax regime for the rich and higher one for the more modest or middle classes".
At a keynote speech at the World Forum Knowledge in Seoul, South Korea, the ex-leader said: "Tax policy must favour investment not rent. I am not against success, but it must not be of those who get richer while they sleep.
"Those who work must see the fruits of their labour and I don't see why one should be generous to taxpayers who know how to invest their money very opportunistically."
Mr Hollande, who famously created a 75 per cent tax on millionaire earners before introducing more business-friendly measures, defended his own record, saying he had little choice but to raise taxes in the wake of the 2008 financial crisis.
"But when growth returned, I reduced taxes on the middle classes, which are the most important, and maintained a relatively high tax rate on the very wealthy."
Globalisation was deepening the divide between rich and poor, he warned, and countries must therefore adopt "policies of redistribution via tax".
Mr Macron issued no verbal response, preferring to let his visit a nursery in a poor Paris suburb on international day for the eradication of poverty do the talking.
But Aurore Bergé, an MP from his Republic on the Move party, said: "We have a former president who speaks to criticise his country from abroad. I find that quite astonishing. He should want his country to succeed."
She called the criticism "indecent" coming from a man who "piled tax on the middle classes" and "over-taxed the rich, which didn't help reduce poverty or kickstart employment in our country".
Relations between the two men were already frosty after Mr Macron snubbed the man who was once his mentor by failing to meet Mr Hollande during a recent visit to the latter’s political base in central France. His prime minister accused Mr Hollande of leaving him with an "insincere" budget.
Mr Macron is said by aides to blame Mr Hollande for the disclosure that he had spent €26,000 on make-up since the election in May, a bill met by taxpayers. The president believed that the leak this summer came from an Hollande loyalist in the Elysée Palace and an adviser said the president had ordered an internal inquiry.
Mr Macron, a former banker, owed his political rise to Mr Hollande, who made him a presidential adviser in 2012 and economy minister two years later. Mr Hollande, 63, thought that his protégé would help him to win a second term of office. Instead, Mr Macron, 39, ran for the presidency himself.
"Emmanuel tripped me up," the ex-president was cited as complaining to visitors by Le Parisien.
His ex-finance minister, Michel Sapin, lashed out the "haughty disdain" of the president and his party in a Le Monde op-ed, in which he slammed his budget as a "moral fault" that goes "against the grain of our history".
Stéphane Le Foll, Mr Hollande's former spokesman said it was disrespectful of Mr Macron to pointedly avoid referring to Mr Hollande by name, calling him "my predecessor".
Another aide suggested that it was poor show that the Macrons hadn't invited Mr Hollande and his girlfriend, the actress Julie Gayet, to the Elysée for dinner. Nicolas Sarkozy and his wife Carla came in July.
"In any case, François wouldn't go," one friend told Le Parisien.
Another was cited as warning: "François will drop a bombshell one of these days, the only question is when."