Prime Minister Najib Abdul Razak has been urged to slash the 'slush funds' of Prime Minister’s Department, which an opposition MP says averaged at RM7 billion a year for the past three years.

DAP's Kluang MP Liew Chin Tong said this needed to be cut down in Budget 2017, to avoid cuts to other sectors such as health, education and welfare.

"Compared with most other budget items, these discretionary development allocations (slush funds) provide scant details of their actual intents and can be utilised virtually by a stroke of the prime minister's pen.

"In Budget 2016, RM3 billion (of the slush funds) was allocated for 'facilitative funds' and you don't know what it's for. That's crazy," Liew said.

He was speaking at a joint press conference with Amanah strategy director Dzulkefly Ahmad in Kuala Lumpur today.

Liew said the slush funds come under the Prime Minister’s Department budget, both of which have been growing exponentially under Najib's administration.

He highlighted how in 2007, during Abdullah Ahmad Badawi's tenure, there were only RM1.1 million in slush funds.

This grew to RM80 million in 2008, and then jumped up to RM631.5 million in 2009, the year in which Najib took office.

Slush funds went into the billions, starting 2011, at RM2.88 billion, with the highest allocation thus far being RM7.16 billion in 2015, he said.

This was cut slightly to RM6.16 billion for the 2016 budget.

Liew said the proposed cuts come amid a tough economy, where further taxation would not only irk the public, but also curb domestic spending, which would slow down the economy.

He said borrowing more funds would further burden the already burgeoning public debt.

Meanwhile, Dzulkefly said despite next year possibly being an election year, the government can't afford to be populist.

"With revenue dwindling, and the 1MDB debt fiasco, Najib needs to be financially prudent," Dzulkefly said.

Liew hopes the government would take into account their proposal before Budget 2017 is tabled on Oct 21.

"There's still time to change it," he said.