The unrest emerged after BT signed a single-agency agreement with Hays IT for the provision of all its contractor resources.
BT told Hays to accept a 3% margin and make every contractor earning more than £15 an hour accept a 12.5% pay cut. This will be the second pay cut in 12 months - a 20% cut was enforced last year. There will also be a £40 per hour cap on wages.
If contractors do not accept the new terms they will be given four weeks' notice.
Some contractors have pledged to leave BT if the cuts are enforced, and concerns have been aired that the move will cause disruption to BT's business and affect quality because the company will no longer be able to hang on to experienced contractors.
One contractor told Computer Weekly, "A lot of contractors are threatening to leave for better rates elsewhere. Many of the key people supporting BT's broadband ordering and provisioning and internet systems are contractors and if many of them leave this will cause BT severe problems."
BT confirmed it had asked for the pay cuts and employee transfers, but a spokesman for the company said, "There will be no effect on quality of work. We are having to meet wage levels that the market dictates."
A spokesman for the Professional Contractors Group said, "In good times rates go up, and in bad times rates go down. We hope this will be remembered when things improve. When that time comes, clients like BT may wish they had retained a little goodwill from their contractors."