SIX years ago Malaysia’s prime minister, Najib Razak, launched a national investment fund that he expected to be “bold and daring”. The assets that 1 Malaysia Development Berhad (1MDB) has since acquired include 15 power stations and desalination plants and some valuable land in Kuala Lumpur, the country’s megalopolis. But lately the fund has struggled to service its debts of more than $11.6 billion. In February it finally repaid overdue loans of about $550m, perhaps by borrowing from a local businessman. It will probably need to find more cash for an interest payment due by the end of March.

The fund’s difficulties have handed Mr Najib’s critics an easy target. They have also made Malaysians curious about how 1MDB has been spending its money. On February 28th Sarawak Report, a website, published e-mails that it claimed cast light on a joint venture that 1MDB formed in 2009 with PetroSaudi, an international oil company. If they are genuine, they appear to demonstrate that a prominent role in setting up the deal was played by Low Taek Jho, a high-living Malaysian tycoon whose association with 1MDB the fund had previously downplayed. The website also said it had obtained messages suggesting that around $670m was transferred out of the venture shortly after it was set up.

The correspondence is among thousands of documents related to 1MDB’s transactions which Sarawak Report claims to possess. It says it will pass them to regulators who can investigate whether rules have been broken. The parties involved deny any wrongdoing. PetroSaudi says all funds from 1MDB went to entities owned by PetroSaudi, and that any other inference is false. 1MDB says that it recovered all the money invested in its partnerships with PetroSaudi, which ended in 2012, along with a profit of $488m. Mr Low has made clear that he has advised the fund “from time to time and without receiving compensation”; a spokesperson says Mr Low provided views on the joint venture but had “no decision-making authority”.

The furore is unhelpful to the government, whatever happens next. As for the broader question of 1MDB’s poor performance, the government stresses that the prime minister has never been closely involved in 1MDB’s day-to-day operations. But he chairs its board of advisers. His standing at home and abroad rests in part on a reputation as a reliable guardian of Malaysia’s money. (He is also the country’s finance minister.) Analysts say that worries about 1MDB are weighing on Malaysia’s credit rating and currency, just as lower oil prices are not good for an energy-exporting economy.

The opposition smells blood. Lim Kit Siang of the Democratic Action Party said that, if journalists really have obtained lots of documents about 1MDB, “we have the makings of the biggest financial scandal in the nation’s history”. Mr Najib is probably more worried about criticism from within his own party, the United Malays National Organisation (UMNO). The fund has long attracted sniping from factions loyal to Mahathir Mohamad, a meddling former prime minister who is itching for Mr Najib to step down.

Talk of an imminent rift within the government subsided a little on March 4th, when the prime minister’s office released a statement asserting that the cabinet is confident that 1MDB has done no wrong. As a further safeguard, Mr Najib says that he has asked the auditor general independently to verify the fund’s accounts. He also promises that the law will be enforced “without exception” should any wrongdoing be proven.

Nevertheless, the prime minister has seemed to be on borrowed time ever since the election in 2013 when UMNO, which has ruled Malaysia for almost 60 years, was very nearly thrown out of power. His approval rating has fallen sharply since then, to a new low of 44% in January. Some had thought that his opponents in the party—now said to be rallying behind Muhyiddin Yassin, a deputy prime minister—would have to wait another year to gain enough support for a leadership challenge. But they may choose to move sooner than that.