Dr Mahathir berkata tidak semua penilaian yang dilakukan oleh Moody's tepat.
Moody's semalam mengumumkan ia menurunkan penarafan penerbit domestik dan mata wang asing senior tidak bercagar Petronas kepada A2 (stabil) daripada A1 (negatif).
It says it has consistently maintained a conservative financial policy and healthy net cash balance that enables it to withstand volatility and shocks in the market.
The global rating agency says the lower ratings are due to its revised cross-sector methodology.
Moody's downgraded Turkey's long-term debt rating to B1 from Ba3 and maintains its negative outlook for Turkey.
Dr Mahathir Mohamad hairan kenapa Moody's mengekalkan penarafan di bawah kerajaan terdahulu yang mempunyai hutang besar sehingga menyebabkan Malaysia mengalami defisit bertahun-tahun.
The finance minister also says SST collections last year were more than projected.
The rating agency says real GDP growth may slow to 4.7% and 4.5% in 2019 and 2020 respectively, after averaging around 5.0% from 2015 to 2018.
Moody’s Investors Service has announced that property loans are the greatest threat to Malaysian banks.
The finance minister is also pleased with Bloomberg’s ranking of Malaysia as No. 1 on the list of 20 emerging economies in the world.
Ratings agency says most companies will be able to manage any tightening of global liquidity, pressure on local currencies or trade friction.
The political secretary to the finance minister says there is nothing contradictory about the views expressed by him and the finance minister on the recent outlook downgrade for Petronas.
National petroleum company says change in outlook is due to Moody’s view that Petronas' financial profile will be at risk of deteriorating if dividend payments remain high in future.
Economist says the government should wait and see how much additional revenue it will get from taxes and increases in oil price before collecting dividends from Petronas.
Moody's berkata tindakan itu disebabkan oleh pengumuman kerajaan bahawa Petronas akan membayar dividen RM26 bilion pada 2018 dan RM54 bilion pada 2019.
The rating agency said this is due to Putrajaya's announcement that Petronas would be paying RM26 billion in dividends in 2018 and RM54 billion in 2019.
The rating agency expects government debt to edge up to 51.1% of GDP in 2019 from an estimated 50.6% in 2018.
The ratings agency downgraded its long-term deposit and senior unsecured debt ratings from A1 to A2.
This is in view of the continuous robust operating conditions in the country and banks' stable fundamentals.
As higher US interest rates and a stronger dollar roil currencies in the region and oil prices spike, governments from the Philippines to Malaysia are facing rising debt.
The rating house says Malaysian government Islamic issues comprised 40% of outstanding government debt at the end of the quarter to March 31, up from 13.9% at the end of 2008.
Moody's rates Greece at B3 positive.
Robust macroeconomic conditions within and outside the country are expected to favour Malaysian banks while helping stabilise asset quality and profitability.
The former prime minister says the ratings agency has maintained the debt ratio declared by the BN government previously.