Fladgate's CEO Adrian Bridge introduced the Croft Pink Port brand in 2008 - the first of its kind. The category of 'rosé port' was then created in July 2009 and opened up the market to competition. He said some producers have been "cutting corners".
Bridge added: "We worked with the IVDP [the regulatory body for port] to create a special category of port.
"Some people have reacted by producing something of inferior quality. We are arguing that although it is a new category, it needs to be a quality one."
Bridge said that "some of the recent products appear to be a blend of red and white port or do not show the sort of quality that should be needed for a special category port".
He added: "As creators of the category we are trying to work with the IVDP in maintaining the standards. Some competitors are doing a good job but some others are cutting corners and this will be a problem for consumers if overall category quality is not maintained."
Bridge said that the aim of creating the new style was to broaden the appeal of the category.
He added that in Holland, the company introduced its Pink Port for €12 a bottle.
"Then [another] product comes in for €6 a bottle," he said.
"This isn't going to excite consumers. It's frustrating that it will confuse consumers.
"We feel that the purpose of the IVDP is to regulate and oversee quality, if it doesn't, it undermines the relationship between the producer and the consumer."
The IVDP's website describes rosé as a "pink-coloured wine obtained by light maceration of red grapes, with no oxidation during preservation. These are wines to be drunk young and are highly aromatic with notes of cherry, raspberry and strawberry. They are soft and pleasant on the palate. They are best drunk chilled or with ice, and can also be served in several cocktails."
Rosé port must be made from red grapes and a spokesperson for the IVDP said: "IVDP is not aware of any mixing of red and white ports. We have paid special attention to this matter."
The Fladgate Partnership is expecting to sell 25,000 cases of Croft Pink in 2011. Bridge added that sales "may go higher as Croft Pink has been taking off in Canada, USA and Brazil."