Tun Dr Mahathir Mohamad has told the BBC that he made only two "minor" demands on Prime Minister Najib Razak - one was on the so-called crooked bridge to Singapore, and the other was to "continue with the railway line" into the Republic.
This was the first time the former prime minister had revealed his unhappiness with Datuk Seri Najib on the handing over of the Keretapi Tanah Melayu (KTM) station, line and land to Singapore in 2011.
Dr Mahathir had spoken many times previously about his unhappiness with Mr Najib for not carrying out construction of a new S-shaped bridge - also called the crooked bridge - to replace the Malaysian side of the Causeway in Johor Baru.
Asked by the BBC in an interview if "personal demands" made on Mr Najib were part of the reason for his split with the Prime Minister, Dr Mahathir answered: "I did ask him why he didn't do what he promised to do, which is to build the bridge and to continue with the railway line and all that.
"But that is a minor thing to me.
"If you don't want to do it, every Prime Minister has a right to his own policy."
The interview centred on the accusations faced by Mr Najib following a report in the Wall Street Journal last Friday that US$700 million (S$943 million) was deposited into his accounts in AmBank.
The Malaysian government led by Mr Najib in 2011 handed over the KTM station in Tanjong Pagar, its land and railway line as part of a bilateral agreement with Singapore.
In exchange, Malaysia received six parcels of prime land in Marina South and Ophir-Rochor.
The KTM trains, which previously stopped in Tanjong Pagar, today stop at the Woodlands Checkpoint.
Mr Najib in recent weeks has accused Dr Mahathir of trying to topple him and said the former prime minister's unhappiness was partly due to the non-construction of the so-called crooked bridge.
But Mr Najib has never before mentioned the KTM deal as a reason for Dr Mahathir's anger with him.
As for the bridge project, Dr Mahathir had wanted to replace the current 1km Causeway road which joins Woodlands to Johor Baru, saying that a bridge would allow sea water to flow freely in the Strait of Johor as a means to clean up the waterway.
When Singapore declined to replace the Causeway, and he had stepped down as prime minister, Dr Mahathir pushed his successors Tun Abdullah Badawi and later Mr Najib, to carry out the project on just the Malaysian half of the Causeway road.
Mr Najib said last month that Malaysia could not unilaterally tear up its side of the Causeway road.
He said Malaysia's Attorney-General had advised him that pipes along the Causeway belong to Singapore's national water agency PUB, according to the 1960s Johor- Singapore water agreements, and that any changes to them without PUB approval would be in breach of international law.