Although IT directors may fear key staff would leave as soon as outsourcing is announced, keeping it a secret is not a good idea, he said.
"We told our people very early on - about a year ago now. It enabled us to get them more involved and to acclimatise them to the deal," he said, speaking at the IT Directors' Forum.
"We held a weekly conference call where the chief executive would often speak to put the whole deal into a corporate context so that it was not just seen as an IT thing. We covered issues such as the likelihood of redundancies and where the cut-off point would be."
The 10-year deal was signed in March and will eventually see 600 Invensys staff transferred to IBM to manage application maintenance, Web hosting, helpdesk and desktop services support.
"About three or four years ago at the height of the Y2K skills crisis companies were afraid to tell their staff about any potential outsourcing deals in case they left," said John Clemmow, managing director at consultancy Quantum Plus.
Clemmow advised Invensys during the negotiations with IBM.
"Now IT staff are happy at the prospect at going to work with a respected, professional supplier such as IBM," he said.
"It is seen as an opportunity to further their careers, to work in pure IT rather than as a member of an IT department."