Network has said from the start of 2009 it will refuse to support any broker that enters into third-party dealing.
If a broker continues to deal in such trading, Network will stop funding.
Jo Elms, brand director of Network, said: “There is still a significant part of the sector that continues to take a short-term approach.
"Broker-to-broker dealing is an enduring characteristic of these less forward-thinking firms.
“Many funders have come out in opposition to third party dealing in the past, but it has not yet been backed up with any concrete stand against the practice.
"That’s what we’re looking to rectify in our new proposition.”