The X Factor mogul spoke out after 1D were named Global Recording Artists of 2013, following the success of their new album Midnight Memories, which included smash tracks 'Best Song Ever' and 'Story of My Life'.
Simon formed One Direction on X Factor back in 2010, after Niall Horan, Liam Payne, Zayn Malik, Harry Styles and Louis Tomlinson initially failed to make it on the show as solo artists.
He took to Twitter to say: "So, One Direction were the biggest selling artists in 2013. I know how much they put into this record from start to finish. Very proud.
"And I also want to thank the other writers, the producers, the team at Syco, Modest, their management, and Sony worldwide.
"And, I have said it before and will say it again… the greatest group of fans. Why can't there be an award for the best fans at the Grammys? Or the Brits? It seems crazy they don't. Is there a reason?"
Niall added: "Incredible news! It's great to have a chart that includes everything from iTunes and record stores, to YouTube and Spotify. Again a huge thank you to all of our fans for such an amazing 2013."
One Direction's Global Recording Artists award was handed down by IFPI. It's a new award that takes into account digital downloads, streaming of tracks and physical sales of their records over the past year.
'Best Song Ever' has been viewed around 200 million times on YouTube, while 'Story of My Life' has clocked up more than 100 million views.
The top ten Global Recording Artists of 2013 were:
1. One Direction
3. Justin Timberlake
4. Bruno Mars
5. Katy Perry
7. Macklemore and Ryan Lewis
9. Michael Bublé
10. Daft Pink
Watch One Direction's video for 'Best Song Ever' below: