France’s Francois Fillon under fire over women’s rights
His rival, fellow Republican Alain Juppe, has urged him to “clarify his position” on abortion.
Meanwhile, a party colleague restated claims he denied her a ministerial post because she was pregnant.
Supporters will choose between Mr Fillon and Mr Juppe on Sunday.
It is the first time the centre right in France has used a US-style primary contest to select a candidate, ahead of the presidential election in April and May.