Several allies and close friends of the French far-right leader Marine Le Pen are due to go on trial in Paris accused of fraud during election campaigns in 2012.

The seven defendants including senior figures in Le Pen’s party, the Front National, which has since been renamed National Rally, will appear in court on Wednesday accused of taking part in a fraudulent scheme to overcharge candidates for party election leaflets.

Each candidate standing for election for the Front National in 2012 was obliged to buy an “election kit”, including posters, leaflets, website design and other campaigning material from a micro-party linked to the central party.

The price for this kit was €16,650 (£14,325), which was close to the legal amount that candidates who scored more than 5% in the first round could later claim back from the state for election costs. But an investigation found that the true cost of the material was around €4,000, allowing its makers – a company run by an old friend of Marine Le Pen – to make a large profit from state funds.

The investigation also claims that the readymade kits did not match all candidates’ election needs.

Party intermediaries are also accused of making a profit from lending funds to candidates for the kits, before the candidates were paid back by the state.

The first allegations relate to elections in 2012. A second investigation relating to elections in 2014 and 2015 will be examined later in court.

The defendants, including a former party treasurer, have denied the accusations. Le Pen’s party has denied any irregularities, claiming the case shows the French justice system is hostile to National Rally. The party’s lawyer said it would fight these “slanderous accusations”.

Le Pen, who is not on trial, told judges during questioning that she played no personal part in organising material for election campaigns and was unaware of the cost of kits.