Ben Hammersley, a Number 10 adviser to the Tech City project, said the draft Communications Data Bill could be turned from a force for good into something more sinister under future governments.
The main aim of the Bill is to give security services like MI5 and GCHQ the ability to monitor email traffic, without actually looking at its content.
However, it is currently being revised after a committee of MPs and peers raised privacy concerns about the bill’s intrusion into people’s lives.
Asked for his views on the new laws, Mr Hammersley said the consequences could be “disastrous” in an interview with Tank magazine.
“I don’t trust future governments,” he said. “The successors of the politicians who put this in place might not be trustworthy.