PhD application for Universities in UK

[Jisi]

Hi, guys! I am currently preparing my Ph.D. application (social science) for universities in the UK. I have found a supervisor who would like to accept me. 

Before this, I have obtained two master degrees during the last three years. I am wondering if the GPA of the first master is very low (64/100), how much extent does it affect my application at the stage of department/college committee considering? My grade of the second master is good (3.6/4.0). Is it too stupid to conceal the experience of my first Master when submitting the application?  

All ideas are appreciated.

[coffeecupanalogy]

I'm also applying to UK!  but I haven't contacted any supervisor yet :/