The reality show, which documents a group of young Welsh people partying and working in Cardiff, are using the posters to promote the third series.
But the posters, that show Natalee Harris, Lateysha Grace and Jenna Jonathan pictured in lingerie flashing their cleavage and bottoms, have been accused of tarnishing the country's reputation.
Critics have said the programme makes 'The Only Way is Essex look like Shakespeare,' and even one of its stars has compared it to a 'live sex show.'
Local MP Chris Bryant has said the show 'drags out every single negative stereotype about Wales.'
'I get a lot of complaints from constituents about the programme,' added Bryant.
'The people who are put on the show are the most unrepresentative people, who hate the Valleys as opposed to the people who work hard here and bring up families beautifully in an area they love.'
MTV have said the sign was built to extend a warm welcome to everyone entering the country, in place of the boring signs usually seen on the roads.
The Valleys season 3 starts on Tuesday 25th February on MTV.