Manila: Senate Blue Ribbon Committee chair Panfilo Lacson on Thursday told Minority Leader Senator Rodante Marcoleta that the panel cannot compel Ako Bicol party-list Rep. Zaldy Co to attend its hearings, citing the principle of inter-parliamentary courtesy.

According to Philippines News Agency, Marcoleta had pressed the committee to invite Co, along with Sunwest Construction - the company he founded - and businessman and former Ilocos Sur governor Luis 'Chavit' Singson, saying their names had been repeatedly raised in testimonies.

'As you know, you have been a congressman for many years. We do not invite or summon members of Congress in the same manner that they don't invite senators to their hearings,' Lacson said.

'It is up to the congressmen or senators concerned to appear before inquiries. That tradition is accorded to the institution," he added.

Lacson explained that only if Co were expelled from the House of Representatives could the Senate formally summon him.

Marcoleta countered that Navotas Rep. Toby Tiangco was previously invited to a Senate probe, but Lacson clarified that Tiangco appeared voluntarily and not through a formal summon.

'Anyway, that's water under the bridge,' Lacson said, noting that Senator JV Ejercito had informed Co about the proceedings and that he could appear on his own initiative.

The committee chair assured that Sunwest and Singson would be invited in the next hearing.