Their guides may not be "rough", but they think Glaswegians are.

Marco Polo, makers of travel pocketbooks, have warned holidaymakers to expect Scotland's biggest city to be the polar opposite of what they see as our "sophisticated" capital.

And they have taken a special side swipe at the local dialect of Scots, referring to it as "rough slang".

The guide book - which is about Edinburgh but has a brief section on day trips to Glasgow - is not entirely uncomplimentary about the Clydeside city.

The English edition, which is translated from German, refers to "the tingling large city atmosphere" travellers can expect after leaving Queen Street station when they arrive from Edinburgh.

But language experts latched on to the insulting reference to "slang". Michael Hance, director of the Scots Language Centre, said: "A dialect can't be rough, that makes no sense linguistically. What does a smooth language sound like?

"My advice to visitors is to go and listen to all the wonderful and different voices in Glasgow and try and not to judge speakers.

"In fact, there are also different and fascinating voices to be heard in Edinburgh too. Enjoy them all because they are special.

"In fact, I am surprised more is not made of our rich variety of languages in our big Scottish cities for tourists."

The Marco Polo guides are following a long tradition of describing Glasgow as rough and earthy and Edinburgh as prim or refined.

The English edition warned visitors to Glasgow from the capital: "You will come across a glaring contrast to Edinburgh: post-industrial charm, rough slang, no-frills urbanity.

"Glasgow is more hectic than Edinburgh and not at all homogenous.

"The unsophisticated but hearty charm appeals to many visitors. Unlike the more refined residents of Edinburgh the Glaswegians don’t mince their words."

The guide's Italian edition was blunter on the contrast between straight-talking, coarse-slang-speaking Glaswegians and "their more sophisticated neighbours".

Ian McDonald, Marco Polo's managing director, said: "I would be sorry if we offended anybody by using the word 'rough'."

He said the guide, which was published last year, simply wanted to show visitors the differences between Scotland's two big cities.

Glasgow City Council turned down the chance to get in to a "rough slanging" match with Marco Polo.

A spokesman instead said: "Whoever wrote this guide clearly enjoyed themselves when they visited Glasgow.

"They’re welcome to return and take the time to appreciate fully what they have already identified as the city’s many charms."