A flawed slogan?

The Plain English Campaign, a lobby group that wages war on linguistic errors through detecting the grammatical mistake said that the slogan misses a verb and ought to read, "Britain forwards not backwards".

Well, the Plain English Campaign is correct but as a thumb rule of construction of a slogan easy, catchy and tricky words should be used to attract common peoples' attention towards a certain matter over which the slogan makers want to raise their awareness and to motivate them to move for appropriate action.

So, the words/sentences used in a slogan may not always satisfy the rules of grammar, not only in English but in other languages too. As such, Blair's party slogan-"Britain forward not back" is acceptable as it sounds more rhythmic than its correct version!