Hi,  my 9 month old dog has just developed some small warts around his mouth area. Will this affect him being shown?  I have tried to research it but can't find any answers.

They might just been juvenille acne spots. 

If there's a staph infection going on, it may not 'affect' him being shown, depending on how bad it is, but it should be cleared up.   We had tis on one puppy in a litter, and our then vet suggested we used neat Johnson's Baby Shampoo, administered on a Q-tip to the area, which worked.   I'd get it checked and if possible treated by your vet?

Will he still be allowed to show whilst having them and if so will he be marked down.

wouldn't think so unless there was so little between two dogs that having spots swung it

This sounds like Canine Papilloma which is a virus and therefore contagious, this article explains it is most common in young dogs:
http://petsci.co.uk/health-care/canine-benign-tumours-lipoma-papilloma-adenoma/

I would definitely see a vet and I would definitely NOT go to any show as as the judge will open the mouths of all the dogs to look at the teeth and therefore can transfer the virus to other dogs.

Hi Goldmali,
Reading the description of these warts and looking at some images, I can be pretty certain it's not that.  His are small and round and perfectly smooth. Almost like lumps.  In fact quite possibly like the previous reply of Juvenile Acne.  They are not in his mouth, more between his mouth and chin.  I have checked in his mouth and it's lovely and clear.  I will get him checked to be on the safe side, but I do feel re-assured that it might not be anything serious.
Thank you all for your help.

Juvenile acne is quite common in some breeds like dobermans

That's good to hear Debs46, and yes, always best to get a vet check to play safe. Good luck with everything.