Former French President Nicolas Sarkozy | Bertrand Guay/AFP/Getty Nicolas Sarkozy in court over campaign finances The former president denies knowledge of alleged overspending.

Former French President Nicolas Sarkozy went to court Tuesday to answer questions over an expenses scandal from his failed 2012 reelection campaign.

Public relations firm Bygmalion is alleged to have charged €18.5 million to Sarkozy's party — then known as the UMP and now called Les Républicains — instead of the campaign, which was subject to a spending limit of €22.5 million.

Sarkozy, who now leads Les Républicains and is hoping to make another run for the presidency next year, has previously denied all knowledge of the affair.

"It will no doubt be hard to believe, but I swear it is the strict truth: I knew nothing about this company until the scandal broke," he wrote in his book, published last month.

Meanwhile, the inquiry has widened to investigate €13.5 million in campaign spending by the UMP, just €3 million of which was declared at the time.

Four other people involved in the 2012 campaign have so far been placed under investigation, including the treasurer Philippe Briand, and campaign manager Guillaume Lambert.

The magistrates may either place Sarkozy under investigation or declare him to be a witness in the case, as they did with former UMP leader Jean-François Copé last week.