The British wife of French conservative presidential candidate François Fillon has been charged in an inquiry into whether she was paid hundreds of thousands of euros for a fictitious job as his parliamentary assistant.

In the latest blow to her husband's faltering presidential bid, judicial sources said Penelope Fillon, 61, had been placed under formal investigation - the equivalent of being charged in the UK - for complicity and concealment in misappropriating public funds, concealed misuse of funds and concealed aggravated fraud.

Welsh-born Mrs Fillon and two of her children were paid for jobs as parliamentary assistants at a cost to taxpayers of about €800,000 (£700,000) over 20 years. Between May 2012 and December 2013, Mrs Fillon was also paid about €100,000 by a literary magazine owned by one of her husband’s friends.

Investigators suspect that she was paid to do nothing both in parliament and at the literary review. She previously told the Telegraph: "I have never been his assistant."

Mr Fillon, 63, was charged earlier this month for misappropriating public funds and misuse of funds. His former successor as MP, Marc Joulaud, has also been charged on the same counts.