French conservative presidential candidate Francois Fillon has said he will not withdraw from the race amid a row over his Welsh-born wife Penelope's well-paid job as his assistant.

Mr Fillon told a news conference that he did not act illegally and he will publish his assets on the internet later.

However, he apologised to the French people for employing his wife, saying that giving work to your family is a practice that is now rejected.

He said: "It was a mistake."

Mr Fillon's popularity has dropped in the past two weeks following revelations by the Canard Enchaine newspaper alleging that his wife was paid 830,000 euro (£717,000) over 15 years.

The conservative candidate said he is "honest", and described the controversy as being like "a clap of thunder".

He said: "I would like to say to the French (primary voters) that their choice cannot be taken away from them.

"They will not be silenced."

Mr Fillon acknowledged that his proposed programme of government, which includes slashing 500,000 public sector jobs, "upsets people".

But he said that "it is the only one that can give confidence back to the French".

The man who served as French prime minister from 2007 to 2012, the chief workhorse under then-president Nicolas Sarkozy, has long had a reputation for being low-key, reliable and morally upstanding.

"I have nothing to hide," Mr Fillon said.

"All acts described (in the media) are legal and transparent," he said.

He noted that employing his wife is not illegal and he is not the only politician to have done it.

Prosecutors are trying to determine whether family members actually did the jobs of parliamentary aides that they were paid for. The preliminary probe involves suspicions of embezzlement and misappropriation of public funds.

The Paris prosecutor's office expanded its investigation last week to include Mr Fillon's son and daughter.

French politicians are allowed to hire family members as aides as long as they actually do the jobs for which they are paid.

Some conservative politicians want Mr Fillon to step down to improve the party's chances of winning France's presidential election. The first vote is on April 23, with the top two finishers competing in a run-off on May 7.

Mr Fillon told reporters: "Yes, I employed my wife as an aide."

He said she was paid an average 3,677 euro (£3,178) per month over 15 years.

"They call this job fictitious," he said, laying out the ill-defined duties of parliamentary aides who work "in the shadows".

Mr Fillon and his family live in an elegant manor in the Sarthe region south-west of Paris. To bolster his reputation he detailed the worth of the building - 750,000 euro (£648,000) - and other holdings, and said he does not have to pay the tax on fortunes demanded of the wealthiest.

He said the scandal grew out of a political conspiracy to take him out of the race, and make it a face-off between far-right leader Marine Le Pen, also a leader in early polls, and centrist Emmanuel Macron.

However, he did not say who would be behind such a plot.

"Nothing will change my mind" about running, Mr Fillon said.

To members of his own Republican party who would like to push him out, he said twice that he is not the candidate of a party, but of the French people.

On Tuesday, senior figures in Mr Fillon's party hold their weekly meeting, a likely place to examine the fallout from the scandal.

There is no procedure in place to put aside his candidacy, however, and no ready replacement for Mr Fillon.

Others running in the presidential race include far-right National Front leader Ms Le Pen, Mr Macron, Socialist Party candidate Benoit Hamon and far-left candidate Jean-Luc Melenchon.

Unpopular Socialist president Francois Hollande has decided not to run for a second term.