The tunnel blasting method involves pre-drilling a series of holes in the underground rock face,loading those holes with explosives and detonating them to blow apart the rock into more manageable pieces to remove.

Mr Parker said blasting was a concern in Leichhardt as the area's heritage homes would be"particularly vulnerable to cracking and damage from the strong vibrations generated by explosives".

"Blasting underneath homes is inherently risky and threatens serious and unnecessary damage over and above the damage that is already being caused by conventional tunnelling,"he said.

However,the WestConnex spokeswoman said blasting was a common tunnel excavation method that had been used"safely and effectively"in other tunnelling projects in Sydney,including the Metro rail line.

"When it is used in areas of hard rock it can significantly reduce the duration of noise and vibration impacts for local communities,compared to using rock-breakers and roadheaders."

Any blasting would be subject to strict conditions and monitored to ensure all vibration levels were within the limits set by the Planning Department and the NSW Environment Protection Authority,the spokeswoman said.

She would not say whether blasting was being considered for other sites in Leichhardt,Annandale,Lilyfield and Rozelle but said it"remains a potential methodology for areas of the tunnel with hard rock".