Governments should break up big multibillion-dollar infrastructure projects into smaller pieces to create more competition and reduce the risks of massive cost blowouts, says new Watpac chief executive Jean-Pol Bouharmont.

Mr Bouharmont, who became the Brisbane-headquartered construction group's CEO in October following its takeover by Belgium's BESIX, said governments would attract more bidders for big $5 billion-$10 billion projects if they separated contracts for tunnelling, stations, property development and maintenance work rather than bundling them together.