Tesco, the UK's largest supermarket giant, has been accused of having a near monopoly in the Highland city of Inverness.
Inverness has three Tesco supermarkets in the city
The city currently has three stores and a fourth is planned in the Holm area.
Local Lib Dem MP Danny Alexander said the retailer's "extremely dominant position" was a cause for concern.
However, Andrew Higginson, Tesco's finance director, rejected claims by Friends of the Earth that the company was manipulating the planning system.
He told BBC Radio Scotland: "It's a lot of rubbish really.
"It would make our jobs a lot easier if that was the case. It's a very long, quasi-judicial and very bureaucratic process.
"It takes us a long time to get planning permission for our stores and we are in no position to manipulate that."
Tesco has just reported record sales over the Christmas holidays. It said like-for-like sales were up by almost 6% on the previous year.
Business leaders in Inverness said the number of large Tesco stores had contributed to the closure of about 20 small shops in the city centre.
Charles Horgan, of the local traders' association, said something had to be done to prevent Tesco from opening another supermarket in the city.
He said another store would complete the "encirclement" of the historic town centre, adding "that's something we're totally against".
Residents in the Holm area have objected to the planned supermarket, saying they feared increased traffic, noise, flooding and crime.
Steven Rodgers, who is campaigning against the new Tesco, said the firm has enough stores already.
Steven Rodgers said local residents opposed plans for a new store
"The general feeling from the community council's point of view is that the development is too large," he said.
"Outline planning permission is in place for a small district centre and its that that we want to get back to."
One customer outside a Tesco store in Inverness said the supermarket chain offered a wide range of goods and services.
He added: "They do most things very well and you tend to come here because it's easy and convenient."
Tesco said its success in Inverness was based on having invested there when many of its competitors were unwilling to do so.
A recent survey indicated that Tesco had a 51% share of the market for groceries in Inverness, the highest rate of penetration for any locality in the UK.