A Bristol MP has urged the Costa Coffee franchise not to open a new coffee shop in Bristol without planning permission.
The branch on Gloucester Road has been refused permission from Bristol City Council, and is appealing against the decision.
In a letter to Costa, Stephen Williams MP (Lib Dem) said going ahead without consent would affect the Costa brand.
A spokesman from Costa said a new coffee shop would have a "re-energising and revitalising" effect on the area.
Plans for the coffee shop on Gloucester Road were rejected in September after a 3,000-name petition was submitted to the council.
Protesters claimed it would "undermine the viability of independent shops", and councillors voted by eight to one to block it.
Mr Williams wrote: "...The applicant is proceeding to fit out the property and intends to open in the coming days, in breach of the current planning control over the site. This has caused great annoyance to many of my constituents."
The company operates a franchise system and has partnered with South West Coffee Ltd, which is run by Bristol businessman Stuart Montgomery.
Costa said: "Our franchise partner has already heavily invested his money in the Bristol area and operates two very popular stores which have gone from strength to strength over the last three years establishing a loyal and regular customer base... a Costa store typically employs between six to 12 people.
"In our experience the opening of a Costa coffee shop often leads to increased footfall to areas, re-energising and revitalising them, therefore bringing substantial benefits to surrounding businesses."