Construction workers on Sydney's cross city tunnel have downed tools after one of their colleagues was crushed to death.

A 42-year-old man was killed late yesterday after rocks fell on him as he operated machinery 40 metres beneath William Street in Sydney's east.

Workers stopped construction and demanded a thorough safety audit of the project. Work was not expected to resume until after an on-site meeting on Monday, the Construction, Forestry, Mining and Energy Union (CFMEU) said.

"We issued an ultimatum to management last night that there be no further
work on the project until seven o'clock on Monday morning," CFMEU state general
secretary Andrew Ferguson said.

"In the interim there'll be a thorough investigation into this particular fatality in the tunnel, and a more comprehensive audit of the project."

"We won't be recommending any undue haste in rushing back to work until we're 100 per cent satisfied there's not partial compliance (but) full compliance with the safety needs of the job," [Ferguson] said.

"We're not satisfied with the performance of this multinational and we intend to ensure they understand the importance of Australian safety laws."