An ancient rule which prevents other markets setting up within six and two thirds of a mile from Dorchester's Cornhill is unlikely to be enforced against small-scale events – but could be used if a rival commercial market was to start up.

The rule, enshrined in a Royal Charter for Dorchester Market, has seldom been evoked – although in the last decade it was threatened to stop a rival market setting up in neighbouring Martinstown.

Dorchester's joint markets panel chair, Cllr Molly Rennie, raised concerns that, if applied, the rule could have consequences for small-scale events, including farmers markets, craft and food fairs in Poundbury, and for the annual Hardy events in High West and High East Streets.

She said that to evoke the rule for those type of events would be unfair, although the panel decided that it will keep a provision in its annual plan to tackle rival markets just in case a threat were to emerge.

The Dorchester Wednesday market, the daily market at Cornhill, Sunday car boot and other occasional markets in Dorchester are overseen by a joint panel made up of Dorset Council and town council representatives, with any profits shared between the two authorities.

Dorchester Town Council has long argued that it should have control of the markets which, it says, was granted to the town by a Royal Charter in 1629, rather than to a wider council area.

An agreement between the then West Dorset District Council and town council to jointly run the markets was settled in 1984 after a 10-year dispute about who should be in charge.