Prime Minister Goh Chok Tong was accused by George Carman QC of "exaggerating" to the court for the purposes of "putting a shine" on his slander case against Joshua Jeyaratnam, the country's 71-year-old Workers' Party leader.
Mr Jeyaratnam faces financial ruin and the effective end of his long political career if the court decides to award heavy financial damages to Mr Goh over remarks made during last December's election campaign.
Mr Goh has contested and won multi-million pound defamation cases against numerous political opponents and newspapers. The prime minister says Mr Jeyaratnam lobbed a political "Molotov cocktail" at his leadership by announcing at an election rally the fact that another opposition figure, Tang Liang Hong, had filed police reports against the ruling party. The reports were later made public on the orders of Mr Goh, who said he had nothing to hide.
"The original defamation, on the eve of polling day, to an audience hostile to the plaintiff, was calculated to whip up emotions and feeling against him and cause the maximum political damage and personal hurt," Mr Goh's British lawyer, Tom Shields, told a packed High Court in his summation.
In a searing attack on the prime minister's motives in bringing the matter to court, Mr Carman, one of Britain's top lawyers, poured scorn on the politician's claim for damages, arguing that the statement to which the prime minister objected was not only true - a fact that in Britain or the United States would in most cases be the ultimate defence - but did the standing of the Singaporean government "no harm whatsoever".
"This case in justice, fairness and in reason should be dismissed in law," Mr Carman urged the judge overseeing the case, concluding that the prime minister's testimony had been "a piece of cheap melodrama" in reaction to "the normal cut and thrust of democratic politics".
He accused the prime minister of attempting to silence his critics through the courts.
Mr Carman contended that Mr Goh and his predecessor Lee Kuan Yew shot themselves in the foot by releasing the contents of the reports over which they were now seeking legal damages."The real loss has been self-inflicted," Mr Carman said.