François Hollande's honeymoon over – in 140 characters

The French press declared President François Hollande's honeymoon to be officially over yesterday – shattered by a public spat between the two women in his life. There was almost universal condemnation of the First Lady, Valérie Trierweiler, for sending a tweet supporting a political rival of Ségolène Royal, the mother of Mr Hollande's four children. The Prime Minister, Jean-Marc Ayrault, publicly criticised the First Lady, apparently with Mr Hollande's blessing. He said that she had to learn to be "discreet" and to "know her place".

The incident – the first big "social media" intrusion into French politics – has been dubbed "Tweetgate" by French newspapers. Delighted right-wing politicians spoke of "Dallas in the Elysée Palace".

Several ministers said, off the record, that the episode was the first serious gaffe of the Hollande presidency and a blow to his carefully cultivated image as a "Monsieur Normal". Though trivial, they said, the incident engulfed Mr Hollande in just the kind of private-public muddle that had damaged the early months of Nicolas Sarkozy's term of office.

Ms Trierweiler, 47, made no public comment. In private, she is reported to be unabashed and unable to understand (despite 20 years in journalism) why her short message filled the front pages of most French newspapers yesterday. President Hollande's unmarried partner, who works for the magazine Paris Match, sent a tweet on Tuesday supporting a renegade Socialist politician who threatens to deny Mr Hollande's former unmarried partner, Ms Royal, a seat in parliament this weekend.

"Best of luck to Olivier Falorni who has done nothing wrong and has battled selflessly for the people of La Rochelle for so many years," Ms Trierweiler tweeted.

Mr Falorni, a long-time ally of Mr Hollande, had refused to accept a decision by his party to "parachute" Ms Royal, a former presidential candidate, into the constituency.

Both he and Ms Royal ran for the seat in the first round of parliamentary elections last Sunday. Both qualified for the second round. With many centre-right voters opposed to Ms Royal, Mr Falorni could win the seat this Sunday. He has refused all demands from party headquarters that he should step down.

The First Lady is reported to have been piqued into sending the tweet by the inclusion of President Hollande's name in a list of second-round endorsements of Ms Royal. Relations between the two were known to be execrable but had seemed to improve lately.

French media said that, by sending her tweet, Ms Trierweiler had simultaneously interfered in an internal party quarrel and publicly displayed her "jealousy" of President Hollande's long-time partner.

One minister tried to laugh the incident off: "The President's partner detests his 'ex' and his 'ex' detests his present partner. What could be more normal than that?" he asked.

But other Socialists complained that the incident had thrown the President's party onto the defensive just as it seemed to be in command. "It's very upsetting," one minister said. "We knew Valerie's attitude [to Ségolène] might cause a problem for François... but we thought they had sorted it out between themselves. Now, it looks as if it's not under control at all."