I can no longer afford to be a member- can I stop my pension contributions?

Yes, but you might want to consider joining the 50/50 section of the LGPS instead of opting out. If you do, you’ll pay half your normal contribution rate and build up half your normal pension. You will retain full life and ill health cover and you can move back to the main section whenever you are ready.
You can use the contributions calculator to check what difference this would make to your take home pay.
If after considering the 50/50 section you decide you would like to opt out, you should complete all sections of the Opt-out Notice and return section A to your employer and section B and C directly to NILGOSC.