New rules governing the sale of indemnity cover to dentists has stoked the ongoing row between the insurance industry and the mutual insurer set up for dentists.

Dentists are now obliged to buy indemnity cover following a rule change introduced by health minister Rosie Winterton.

Two options exist - discretionary indemnity from the mutual Dental Protection, part of the Medical Protection Society, and cover bought on the open market, through brokers such as Howden.

Market providers say discretionary cover offers less protection. But the discretionary providers argue that its cover is superior.

Kevin Lewis, director of Dental Protection, said of the new rule: "This will come as a bitter disappointment to those lobbying so hard to deny doctors and dentists the option of discretionary, occurrence-based indemnity."

He said 70% of UK dentists chose discretionary indemnity over insurance policies, claiming these "often contain rigid terms that can leave them exposed".

A spokeswoman for former mutual Medical Defence Union, which operates insurance provider The Dental Defence Union, said: "Insurance is the only way to ensure dentists have the proper security."

Howden's Dr Paul Lambden said: "Discretionary policy providers have an absolute right to decline a claim."