Finance Minister Lim Guan Eng has answered former prime minister Najib Abdul Razak's challenge for Putrajaya to explain how it came to the RM100 billion cost estimate for the cancelled Kuala Lumpur-Singapore High-Speed Rail (HSR) project.

Najib had rubbished the RM100 billion figure, saying his administration had estimated the cost of just RM72 billion.

Lim, however, said the new estimate takes into consideration interests incurred to finance the project.

"Please be truthful, when you want to make statements don't think you have the facts.

"In the past, you may have the facts, but now we have the facts.

"If you include interest component (the HSR cost) is way above RM100 billion," he said at a press conference in Putrajaya today.

He then cited a quote popularly attributed to Abraham Lincoln that "you can fool all the people some of the time and some of the people all the time, but you cannot fool all the people all the time".

Putrajaya had scrapped the HSR mega-project as part of a cost-cutting exercise and the government is expected to pay Singapore RM500 million in compensation for the move.

Lim also cast doubt on reports that the cancelled MRT3 project would not have been financed by the government.

"Are you sure? You shouldn't listen so much to BN," he said.

It was reported that the MRT3 was to have used a different financing model compared to the MRT1 and MRT2 projects in being one which would require the contractors to seek their own financing.

It was estimated the MRT3 would cost between RM40 billion to RM50 billion.

The circle line project was intended to link up the completed MRT1 running from Sungai Buloh to Kajang and the ongoing MRT2 running from Sungai Buloh to Putrajaya.