Besieged by a growing legal firestorm arising from an alleged affair, CNRP leader Kem Sokha yesterday ignored a summons to appear at court while calling out authorities for wasting the public’s money, resources and time to probe his personal life for political ammunition.

In his first direct response to the ballooning scandal, Sokha told a gathering of 50 youth supporters at the opposition’s Phnom Penh headquarters that his personal life had long been used for political attacks.

“Over my struggle for 20 years, there has not been any mandate, any year, they have not provoked me,” said Sokha, who avoided referring to the ruling Cambodian People’s Party by name.

“Since I started in politics in 1992 and 1993, they have provoked me until now. These aren’t small stories but like a storm. But it’s my individual story, why have they pounded me so much?

“Why have they spent time, used institutions, spent money and used people to pound me so much?”

Sidestepping the issue of the affair itself, Sokha, said his “work for the nation” made him a target.

The opposition leader faces allegations of procurement of prostitution and a defamation claim related to the affair, which was brought to light after covertly recorded phone conversations, said to feature him speaking to at least three mistresses, were leaked online.

He yesterday boycotted a hearing at Phnom Penh Municipal Court related to the latter case, which was brought by social media celebrity Thy Sovantha over disparaging comments made in one of the recordings.

Sokha’s lawyer, Ang Udom, declined to comment beyond confirming his client had not appeared for questioning.

On Tuesday, Anti-Corruption Unit President Om Yentieng, a close confidant of Prime Minister Hun Sen who has zealously probed the scandal, warned that Sokha would face arrest if he failed to show up.

Reached yesterday, Phnom Penh deputy prosecutor Keo Socheat, who is handling the case, directed queries to court spokesman Ly Sophana.

“The deputy prosecutor is holding the case and needs to check the legal procedure before taking action,” Sophana said.

Critics say the swift and growing case against both the opposition members and civil society workers is being driven by the CPP to crush its political rivals and critical voices, though ruling party spokesman Sok Eysan again denied this yesterday.

Related: Fading mirage of the CPP

Four workers from rights group Adhoc, a UN worker, an election official and an opposition commune chief, Seang Chert, have been detained and charged with conspiring to bribe Khom Chandaraty, one of Sokha’s alleged mistresses, to deny the affair.

A protest against the group’s imprisonment earlier this week dubbed “Black Monday” ended with eight people being detained for several hours.

Two CNRP lawmakers have also been summonsed for questioning linked to the procurement of prostitution claim.

Yesterday, a scheduled hearing for Chert was delayed until May 18 because the court “was busy”, according to the commune chief’s lawyer, Sam Sokong, who said he would lodge a bail application after that date.

The current political situation was brought up yesterday during a meeting between US Ambassador William Heidt and Foreign Minister Prak Sokhon, according to US Embassy spokesman Jay Raman, who said the envoy’s visit was a courtesy call to the newly appointed diplomat.

“We continue to express our deep concern in public and private about the recent arrests of Adhoc staffers and others,” Raman said, via email.

Raman said Heidt also emphasised the US had no involvement in the “Black Monday” campaign, which government officials have equated to a “colour revolution” aiming to topple the government.

Speaking to reporters after the meeting, Foreign Ministry spokesman Chum Sounry said he believed Heidt’s comments.

“He made clear that the US understands very clearly what it should do and what it should not,” Sounry said.

Since the scandal has unfolded, Sokha and the party have largely adopted a “don’t respond” policy. On condition of anonymity, however, an opposition insider yesterday said the strategy of staying quiet and holding out for the elections had “backfired” and needed to change.

“It’s the wrong assumption. The CPP has shown in the past they are not trustworthy, they will not deliver on their promises,” they said, using a boxing metaphor to continue their point. “The CPP keeps hitting and hitting. Before, the CNRP could block, but now both hands are down and the CPP is pounding . . . We don’t answer, we don’t respond . . . and it’s not working.”

The insider said that while injustices dealt to the party may draw sympathy from the electorate, supporters needed to see courage. “People will lose trust and become hopeless and think [the CNRP] cannot deliver. We have to go on the offence, in the 1990s, Rainsy was known for confrontation and posture, and it was successful.

“We need to do something different, and confrontation might be it. Not physically but verbally, confront the injustice and keep speaking up about what is wrong and what is right.”