MADRID, July 23 (Reuters) - Spanish former Prime Minister Jose Luis Rodriguez Zapatero said on Thursday that €1.3 million ($1.5 million) of jewellery seized by ‌police as part of an investigation was a personal gift he ‌received years ago and was never intended for financial gain.

Zapatero, who was prime minister from 2004 ​to 2011 and remains an influential figure in the governing Socialist Party, is under investigation over alleged influence-peddling, accusations he denies. The case is one of a series of corruption scandals affecting the party and piling political pressure on Prime ‌Minister Pedro Sanchez's government.

In his ⁠first interview since being placed under investigation two months ago, Zapatero told Spanish public broadcaster TVE that the jewels found ⁠during a search of his office were "a personal courtesy gift" that had been stored for years with other family valuables.

The jewels were unrelated to his political activities ​and their ​origin and handling would be fully ​explained before a judge, he said. ‌He rejected suggestions they reflected any attempt at personal enrichment.

Investigating Judge Jose Luis Calama opened a separate probe into the jewellery, whose origin remains undocumented, according to investigators. An auction house provisionally valued them at about €1.3 million ($1.5 million), though Zapatero disputes that estimate.

Zapatero said that, with hindsight, he might not have ‌accepted the gift.

"Looking back, I would have ​probably taken another decision," he said.

The jewellery is ​one strand of a wider ​investigation that also includes allegations that Zapatero profited from using ‌his influence to secure the state-backed ​rescue of airline Plus ​Ultra. He also denies those allegations.

The opposition People's Party (PP) dismissed Zapatero's comments on Thursday.

PP spokesperson Ester Muñoz said Zapatero "has every right to lie, ​but he has not ‌answered any of the questions or doubts Spaniards had" about the case.

($1 = ​0.8779 euros)

(Reporting by Emma Pinedo; additional reporting by Javi West ​LarrañagaEditing by Charlie Devereux and Gareth Jones)