Credit cards belonging to the disgraced former prime minister of Malaysia were used to spend more than $800,000 at a jeweller in Italy in a single day, a court in Kuala Lumpur has heard during his corruption trial.

The spending spree took place at De Grisogono, a Swiss luxury jeweller, in Italy on 8 August 2014 where items worth 3.3m Malaysian Ringgit ($803,000 or £645,000) were purchased on Najib Razak’s Visa and Mastercard platinum credit cards, the court was told.

A few months later, 466,000 Malaysian Ringgit ($108,000) was spent at a Chanel boutique in Hawaii and 127,000 Malaysian Ringgit at Bangkok’s luxury Shangri-La hotel using the same credit cards. All the payment were made from Najib’s Ambank account, prosecutors said.

The credit card bills were presented as evidence in the trial of the former Malaysian prime minister, who was toppled from power in May last year and is now facing dozens of charges for corruption, misappropriation of funds and abuse of power linked to government fund 1MDB.

The trial, relating to the misuse of a subsidiary fund called SRC, is the first of several that Najib is due to face in the coming months for his alleged role in the scandal.

Under Najib’s watch, it is alleged upwards of $4bn was embezzled from 1MDB and spent around the world, funding films, yachts, real estate and celebrity parties. It is alleged $681m (£516m) went into Najib’s personal bank account and was used to fund the lavish spending habits of Najib and his wife Rosmah Mansour. Najib and Rosmah, who is also facing multiple charges, both deny all wrongdoing.

The opulent lifestyle of Najib and Rosmah was a source of much resentment in Malaysia during Najib’s time as prime minister and after their arrest there was a collective revulsion when raids on the couple’s family properties uncovered a cache of luxury goods worth $273m, including 1,400 necklaces, 567 handbags, 423 watches, 2,200 rings, 1,600 brooches and 14 tiaras, the biggest seizure in Malaysian history.

Najib defended the credit card spending as purchases for official purposes. “This spending is for gifts to a senior member of the royalty of a government and their entourage that has good relations with our country,” Najib wrote in a Facebook post late on Monday. He did not clarify which royal had received the jewellery. “It is a norm to give gifts to leaders of other governments.”