Fillon payment inquiry: What you need to know

He was once the favourite to win the French presidency, but centre-right candidate François Fillon's fortunes have been dramatically dented by a "fake jobs" row.

His Welsh-born wife, Penelope, has become caught up in a controversy surrounding her work as a parliamentary assistant.

As the presidential race hots up, Mr Fillon, a one-time prime minister, is under judicial investigation and has spoken of a "political assassination".

Nothing, say François Fillon and his wife, who insist everything was above board. But prosecutors have decided there is sufficient evidence to open a full judicial inquiry into abuse of public funds and the examining magistrate has placed both under formal investigation.

The question is: did Penelope Fillon do the work she was paid for? Satirical weekly Le Canard Enchaîné alleged in late January that she did not - and got €831,400 (£710,000; $900,000) for her trouble.

She was employed as her husband's parliamentary assistant from 1988-90 and again in 1998-2002 and then by his successor as an MP, Marc Joulaud, from 2002-2007. He too has been placed under formal investigation.

Penelope Fillon worked again for her husband from 2012-13. That would all be very well if she actually did the work, but reports suggest she did not have a parliamentary pass or a work email.

The allegations do not stop there.

According to Le Canard, Mrs Fillon also pocketed €100,000 for writing just a handful of articles for a literary review La Revue des Deux Mondes, owned by a billionaire friend of the family, Marc Ladreit de Lacharrière.

Mr Fillon is also being investigated for allegedly failing to declare a tax-free €50,000 loan from the billionaire which he has since repaid.

The inquiry widened in March to include two luxury suits worth some €13,000 that were bought for him by a friend. It has also emerged he accepted two watches worth more than €10,000 apiece.

And then there are the children. Mr Fillon will have to explain why Marie and Charles Fillon were paid by their father's office for legal work. Le Canard alleges they were not yet qualified lawyers.

Mr Fillon, 62, said initially that he would resign if he was placed under formal investigation.

And yet he is fighting on regardless, arguing that he is being unfairly targeted. "The closer we get to the date of the presidential election, the more scandalous it would be to deprive the right and centre of a candidate," he said.

That change of mind prompted key allies to abandon him. But when Bordeaux Mayor Alain Juppé ruled himself out as a replacement the party leadership swung behind Mr Fillon.

Opinion polls however suggest the one-time favourite for the presidency is now third in the race and unlikely to reach the second round on 7 May. If somehow he were to make the runoff, he could still win the race.

François Fillon has complained of an "institutional coup d'état" orchestrated by the left, and of a "black cabinet" going all the way to the current president, François Hollande.

There may well have been a campaign to target him, and where Le Canard sourced its information is unclear.

But the judiciary is pushing ahead with a full inquiry.

Mr Fillon is under formal investigation for abuse of public funds and receiving bribes. Penelope Fillon is being investigated for complicity.

Mr Fillon complains of a "political assassination", and of being in the cross-hairs of magistrates and media. He will need more than rhetoric to help his campaign.

When summoned by investigating magistrates, Mr Fillon refused to answer questions but read a statement denying the allegations against him and his wife. "Yes I employed my wife and the reality of her work is undeniable," he told them. "Throughout these years, my wife worked by my side and by the side of my successor to ensure perfect continuity."

Asked by French TV about the work that his wife had done, he said: "She corrected my speeches, she received countless guests, she represented me in protests, she passed on people's requests... she did it willingly for years."

Penelope Fillon said in an interview, external that her husband "needed someone to carry out his tasks. If it hadn't been me, he would have paid someone else to do it, so we decided that it would be me". Family lawyer Antonin Lévy explained that Mr Fillon had no constituency office so Penelope Fillon fulfilled the role from home.

The Fillons' lawyers have reiterated the family's innocence, promising that it would be recognised eventually by independent judges.

Well, yes he does. It is really not unusual for French MPs to employ a member of their own family. French website Mediapart worked out that 115 out of 577 MPs did just that, either on a full- or part-time basis.

And in France there is nothing illegal about it, assuming they actually do the work.

What might prove awkward is that few people have any recollection of Mrs Fillon doing any work. And remarks she made in 2007 to the Sunday Telegraph, external do little to help. "I've never been his assistant or anything of that kind... I didn't handle his PR either."

Mr Fillon dismissed the remarks as out of context, and said first and foremost she had been a partner rather than a subordinate.

Michel Crépu, an ex-editor of the literary review that apparently paid her €100,000, told Le Canard Enchaîné that she published two or three literary reviews but he had never met her and "never seen her in the office".

In her defence, Penelope Fillon said she "produced reading notes" for the review's owner.

The Republicans appear in disarray and François Fillon's main rivals in the presidential race are the clear winners so far.

One is far-right National Front leader Marine Le Pen, who has her own "fake jobs" row to deal with. The FN is under investigation for alleged misuse of EU funds and Ms Le Pen has refused a police interview because she has immunity as a member of the European Parliament.

At least three FN officials, including her personal assistant, are under judicial investigation in France over the affair.

So the rival with perhaps most to gain is Emmanuel Macron, the centrist, young ex-economy minister, who has come from nowhere and is neck and neck in the polls with Marine Le Pen for the first round on 23 April.

If Francois Fillon fails to make the run-off, then he would be favourite to win the presidency.