Khairy Jamaluddin has chided Prime Minister Dr Mahathir Mohamad for stating that he was ashamed over unpaid National Higher Education Fund Corporation (PTPTN) loans.

"Don't be ashamed sir. They are not supposed to repay (the loans) until their monthly income reaches RM4,000 a month.

"Plus, many of those who were 'blacklisted' were taken off the list by your government," he wrote on Twitter.

He was referring to the Pakatan Harapan government's pledge to postpone the repayment of PTPTN loans for all graduates whose salaries are below RM4,000.

This is yet to be implemented as a mechanism has not been worked out, although the government has taken loan defaulters off the immigration blacklist.

Earlier today, Mahathir said he was ashamed that PTPTN borrowers who earned enough to make repayments have not done so.

He said those who earned RM2,000 should be able to repay at least RM100 per month to the fund.

Unpaid PTPTN loans have reportedly reached RM36 billion.

In a separate tweet, Khairy, who was the former youth and sports minister, asked how Mahathir planned to increase the number of PTPTN repayments.

The Rembau MP has been critical of Harapan's plans for PTPTN, urging the government to be cautious and to avoid a situation where the government would have to take loans to finance PTPTN due to low revenue collection.