French centre-right presidential candidate Francois Fillon has lashed out at his critics amid an investigation into payments he allegedly made to his wife.
Investigators are looking into whether he paid large sums to his wife Penelope for "fake jobs".
Mr Fillon, who denies any wrongdoing, said the accusations were intended "to destroy" him and the Right.
The ex-PM is facing mounting pressure to quit the presidential race.
Prosecutors on Thursday widened the investigation to include payments allegedly made to two of his children.
A French TV channel also screened extracts from an interview with his Welsh-born wife in 2007 in which she told British media that she had never worked as his assistant.
"It's not justice they are seeking, it's to destroy me," he told a political rally in Charleville-Mezieres, in Ardennes in northern France.
"And beyond me, to destroy the Right and its vote," he added.
What is it all about?
Penelope Fillon has been accused by satirical weekly Le Canard Enchaine of being paid hundreds of thousands of euros for work she may not have done.
The couple have said she was legitimately employed as his parliamentary aide, and her lawyer, Pierre Cornut-Gentille, said she handed over evidence of the work she did.
But on Thursday evening, France Televisions aired an old interview with his wife in 2007 - when Mr Fillon was prime minister - in which she said she had never worked as his assistant.
His lawyer, Antonin Levy, told L'Express newspaper that the remarks had been "taken out of context."
Now, investigators are also expected to look into payments of more than €80,000 (£69,000; $86,000) made to Marie and Charles Fillon, when their father was a senator between 2005 and 2007.
Mr Fillon said his children were paid as lawyers, for specific tasks. But neither was a qualified lawyer at the time. According to Le Canard Enchaine, they drew pay cheques not for assignments, but for two full-time jobs.
What is the impact on the race?
Mr Fillon said he would fight the accusations "to the end".
Republican MP Philippe Gosselin said an open letter was being drawn up by some members calling for him to be replaced by his 71-year-old rival Alain Juppe if he decides to stand aside.
Republican lawmakers who support Mr Fillon published their own letter in the Le Figaro newspaper, denouncing what they called an "attempt to kill" his candidacy. The 17 names included stalwarts such as former finance minister Francois Baroin.
Until recently, Mr Fillon was the favourite to win the presidency in elections in April and May. He has now slipped behind far-right leader Marine Le Pen and centrist Emmanuel Macron, being defeated in the first round, a poll suggested on Wednesday.
The poll showed Mr Macron easily defeating Ms Le Pen in the run-off.
What will happen to the Republicans?
Support for Mr Fillon is eroding among his own party.
Mr Juppe, who lost to Mr Fillon in the Republican primary race, says he is not a "Plan B", even though his supporters may have other ideas.
According to the lawyer in charge of the centre-right primary, Anne Levade, there is no provision for anyone pulling out. But if it did happen the interested parties would have to make a decision on how to proceed.