ATHENS – The brother and sister of Greek Prime Minister Alexis Tsipras have denied winning a 1.1-million euro ($1.29 million) state contract by submitting fake documents that their company’s social insurance payments were current.

There was no explanation why the siblings of a Prime Minister were allowed to make a bid on state work and his brother, Dimitris, and sister, Zanet, said there was no funny business around their construction firm Diodos, getting the contract.

New Democracy, the major rival to Tsipras’ Radical Left SYRIZA, demanded answers over the questions that arose including a law passed in 2016, the government’s second year in power, that applied a statute of limitation to the case, preventing any probe of the Premier’s siblings.

The pair threatened to sue if New Democracy, which has taken big leads in polls after Tsipras reneged on anti-austerity promises, keeps up the barrage of questions over their contract.

“Because over the past few days ND is mudslinging and leaking vile charges against us, through its friendly press, we would like to emphasize that libel is a civil and criminal charge; it is not justified by any opposition fury, and will be dealt with by the courts, where every law-abiding citizen can seek recourse.”

Ironically, they raised the question of suing for libel at the same time Tsipras has claimed 10 rival politicians took bribes from the Swiss pharmaceutical company Novartis without providing any evidence beyond his accusations.

New Democracy spokeswoman Maria Spyraki renewed the questions around the case that saw Tsipras’ brother indicted in 2015 before she charged the law was changed to prevent him from being prosecuted, with no explanation why that wasn’t obstruction of justice and as she said the contract was won through fake social security documents.

A claim was also made by the right-leaning Parapolitika paper, which claimed that Dimitris Tsipras and Zanet Tsipras’ company received preferential treatment to settle a loan of 243,544 euros ($285,938), giving them 67 years to repay it.

“How is it that a company which by chance belongs to (Tsipras’) siblings is paying just 300 euros ($352.24) a month?” ND said. SYRIZA charged New Democracy leader Kyriakos Mitsotakis was orchestrating the attack.