She almost scaled the summit of French power but these are difficult days for Ségolène Royal, the former Socialist presidential candidate. Last week she was struggling to convince police that it was worth investigating a series of mysterious break-ins at her apartment.

“In a democracy you would think that it would cause a scandal, that it would provoke some condemnation from the authorities,” she said in an interview with The Sunday Times, referring to the break-ins and the possibility that she is being bugged.

“But no,” she went on. “It amused them [the police]. Their reaction was very sarcastic. I think it’s very strange.”

Abandoned by many of her former supporters and separated from her companion of three decades, Royal, who lost the presidency to Nicolas Sarkozy, seemed a lonely and vulnerable figure last week as she outlined the startling events in her home and prepared to do battle for the leadership of her troubled Socialist party.

François Hollande, the party’s first secretary for the past decade - and the father of Royal’s four children - has promised to relinquish the post in October so that a successor can be elected by party activists at a conference in November.

Royal, 54, wants the job. She also wants to be selected as the party’s presidential candidate in 2012. Success is by no means certain, however, despite the glow that lingers around her as the first woman to have come so close to the presidency.

Her claims that the entourage of Sarkozy, with whom she repeatedly locked horns in the election campaign and whose reformist policies she fiercely criticises, might have had something to do with the intrusions at her flat have raised eyebrows not only among “Sarko” supporters. In Socialist ranks there is embarrassment over what sounds, to some, like paranoia.

“What can you say to defend Ségolène Royal?” asked Libération, the leftist daily. “Nothing.”

A spokesman for Sarkozy’s centre-right party suggested that Royal might have “blown a gasket” and another centre-right MP said that she had reached the “wastebasket level of politics”.

François Fillon, the prime minister, said: “Madame Royal is losing control of herself.”

Seated on a sofa in a bookshop in Marseilles last week, Royal, wearing a bright floral-patterned dress, expressed anger at all the criticism. “These are things that should be taken seriously,” she snapped.

In the latest incident in June, intruders had rummaged through her papers and other belongings but did not steal anything, she said. Her apartment had been ransacked twice before, including once just before last year’s election. What is more, computers had been stolen from the flats of friends and assistants.

“It’s a political matter when the home of one of the principal opponents of the president is ransacked,” she said.

Olivier Besancenot, the “red postman” and firebrand head of the Revolutionary Communist League, has also complained of suspicious harassment. Royal’s supporters argue that, however far-fetched it may sound, the possibility of government involvement cannot be dismissed in a country with such a history of political dirty tricks.

François Mitterrand, the last Socialist president - and Royal’s political mentor - kept a secret unit in the Elysée Palace to eavesdrop on political opponents.

Royal was in Marseilles to sign copies of her book, If the Left Wants Ideas. It is a collection of essays written with a sociologist and intended to counter criticism that despite her attractive image, Royal lacks coherent policies.

She beat several male rivals to the party’s nomination as presidential candidate and has often blamed their subsequent lack of support - and the sniping of Hollande, who harboured his own presidential ambitions - for complicating her battle against Sarkozy.

“The candidate did not find a shoulder to lean on, to let go, to cry when things were tough or to laugh in joyful times,” Royal wrote about herself in her memoir. She announced her separation from Hollande, who was having an affair with a journalist from Paris Match, in a radio interview shortly after her election defeat.

Last week she said that she did not want to dwell on the past but reiterated her complaint that party divisions had cost her the election. “I had the support of the party’s base, but not the summit,” she said.

She hopes that the base is still with her in the next battle, even if the “elephants”, as the party’s predominantly male leaders are known, remain opposed to her.

The polls for the leadership contest are not favourable, however, with one showing her trailing far behind Bertrand Delanoë, the chain-smoking gay mayor of Paris who consistently ranks as France’s most popular politician.

Nevertheless, Royal’s trenchant attacks on Sarkozy, whom she accuses of pandering to the rich and breaking electoral promises to the poor, go down well with the most left-wing Socialist party in Europe.

“Public services are being cut with no clear explanation,” she says. “People are very disappointed.”

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