Malaysian prosecutors on Thursday slapped an additional 25 charges on the former prime minister Najib Razak over his alleged links to the multibillion-dollar scandal at state investment fund 1MDB, leaving the 64-year-old facing the prospect of spending the rest of his life behind prison walls.

The new charges piled pressure on the former leader as he reeled from a tumultuous fortnight in which unrelated money-laundering charges were laid against his lawyer Shafee Abdullah and key allies left his United Malays National Organisation (Umno) political party, which was the key player in the Barisan Nasional coalition that had run Malaysia for 60 years.

And things for Najib could be about to get worse – according to local media reports, attorney general Tommy Thomas is preparing charges against one of his family members, widely believed to be his wife Rosmah Mansor.

Of the 25 new charges, four are for corruption, nine are for money laundering, seven for transferring illicitly obtained funds, and five for the use of ill-gotten gains. Najib pleaded not guilty.

The new charges are linked directly to the 1MDB scandal. Investigators have claimed that some US$700 million of 1MDB funds were wired into Najib’s bank accounts. 1MDB was 42 billion ringgit (US$10 billion) in debt at the time of the scandal.

The most serious of the 25 charges carry a maximum 20-year jail term. Najib is already facing up to 20 years in jail regarding four earlier charges levelled against him for alleged money laundering at SRC International, a former subsidiary of 1MDB.

Najib arrested, his allies have quit. Is Umno dead and buried?

Shafee, who posted the remainder of his 1 million ringgit bail yesterday, remains Najib’s lead counsel.

The latest set of charges come in the same week as the international release of a highly anticipated book on the scandal, seen as Malaysia’s biggest-ever corruption case.

Billion Dollar Whale: The Man Who Fooled Wall Street, Hollywood, and the World, which is already sold out in Malaysia, alleges that fugitive businessman Low Taek Jho – also known as Jho Low – engineered the 1MDB scandal with Najib’s assistance.

In an interview with an online news portal, author Tom Wright said although initially it seemed as if Najib was at the centre of the corruption, “Jho Low was really the only character who had a 360 [degree] view of what was going on” – although Najib was, he added, far from blameless.

The book details Jho Low’s extravagant expenditure, including the purchase of superyacht the Equanimity, Cristal-fuelled parties in Las Vegas and Saint-Tropez, expensive jewellery gifted to models, and a birthday party that saw Britney Spears jump out of a cake to serenade Jho Low and his guests, who included the likes of Jamie Foxx, Kanye West, Paris Hilton and Leonardo DiCaprio.

Arrest warrants for Jho Low have been issued in Singapore and Malaysia; the book’s authors believe he is hiding in China.

Malaysia’s 1MDB scandal: a Razak family affair?

Najib’s spiralling fortunes are in stark contrast with those of his former opponent, democracy icon Anwar Ibrahim.

After the Pakatan Harapan coalition formed a government following its shock election win over Barisan Nasional in May, Anwar was granted a royal pardon and charges of sodomy and corruption that had seen him jailed were expunged. Anwar has always contested that the charges were trumped up by his political rivals to discredit him.

Anwar is now seen as the country’s prime minister in waiting. Prior to the election he had made a pact with Mahathir Mohamad – the current prime minister – that if their coalition were to win power Mahathir would hand over power to Anwar within two years.

Anwar has since taken steps to realising that agreement, announcing his intention to re-enter active politics and engineering a by-election in Port Dickson after the sitting MP, one of Anwar’s party members, resigned.

The Port Dickson by-election was officially announced by the Electoral Commission on Thursday – 20 years to the day Anwar was first arrested following his sacking as Mahathir’s deputy during Mahathir’s first stint as prime minister. Anwar must win this by-election, to be held on October 13, to gain a seat in parliament, a prerequisite for becoming prime minister.