It has been a difficult few months for Malaysian Prime Minister Najib Razak, due to multiple graft investigations into the 1MDB fund he set up. Indeed, he has focused on saving his own skin, after it was revealed he and his wife Rosmah Mansor, had reportedly spent hundreds of thousands on anti-ageing products.

Leaked documents from Malaysian enquiries into the scandal-hit state fund indicate that over 1.15m ringgits (£212,000; $238,000) were spent on hormone-based treatments, apparently for the country's first couple, via a clinic in Kuala Lumpur.

The Sarawak Report, a news website that is a thorn in the side of the Malaysian government, states how investigators found the money was spent on "two sets of medication type External Plant Serum Food Application based softgel GH-9 Honey and Honey Food GH-9 Soft Gel".

It said that they cost "$159,000 each set for the use of B1 and wife", with B1 apparently referring to the prime minister, who is 63. His wife is 64.

The website said that a cheque, "which clearly bears the now familiar signature of Prime Minister Najib Razak", was made out to an alternative medicine clinic in Kuala Lumpur called the Sahamm Society for the Advancement of Hormones and Healthy Ageing. It specialises in growth hormone therapy to combat the signs of ageing.

The Malaysian Anti-Corruption Commission (MACC) is looking into local diversions of money from the 1MDB fund, which Najib set up in 2009 to increase investment in the South East Asian country.

Other countries have also launched investigations over claims that hundreds of millions of dollars from 1MDB went into Najib's personal account.

The US Justice Department filed a civil lawsuit to seize more than $1bn (£760m; €910m) in assets allegedly stolen from 1MDB earlier in July. Although Razak was not named in the suit, there are references to "Malaysian Official 1", and people close to the investigation say that official is Najib. His stepson Riza Aziz and Low Taek Jho – better known as Jho Low – were named.

There have already been many claims of lavish spending by Malaysia's first couple. The Wall Street Journal, which first uncovered the 1MDB scandal, reported claims they had spent $15m (£10.5m, €13.3m), on luxury items like clothes, jewellery and cars.

Najib denies any wrongdoing and says he is the victim of a political smear. Malaysia's communications and multimedia minister, Salleh Said Keruak, said in July that the claims against the prime minister needed to follow due process, adding: "No one should rush to judgement before allegations are proven in court."

Malaysia Prime Minister Najib Razak
Pictured here in 2011, Malaysia Prime Minister Najib Razak and his wife Rosmah Mansor. The 1MDB state fund that Najib set up is at the centre of an international graft probeGetty