A council warned taxi drivers today they faced suspension if they put up St George stickers and signs saying they speak English in their cars.
A minority of licensed cabs in Southampton have put the signs up because they claim passengers have complained to them that some drivers cannot speak English.
The matter came to a head in a meeting with drivers and the city council last week when some drivers told the council of the alleged problem.
Now the city council has said any cab that has the sign or a St George flag put up will have their licence suspended if they do not take them down within seven days.
This is because they need the permission of the authority to put up any sign.
It is also asking members of the public to report any such signs.
Councillor Royston Smith, deputy leader of Southampton City Council, said: "Members of the public and the taxi trade have expressed their concerns to us that these stickers are inappropriate so we are asking any taxi drivers in the city who are displaying these to take them down.
"In Southampton we take a really proactive approach in making sure our taxi drivers can communicate well to customers and we are satisfied that all our drivers have good enough communication skills to do just that.
"We are one of the few authorities in the country to require all new taxi drivers to pass a basic written skills test before they can get a licence, and then they need to pass a level 2 BTEC qualification.
"All our taxis have also been fitted with safety cams, so not only are we ensuring top quality customer service, our taxis will also be some of the safest in the country."