Accor Euro 2005 boost fade on idle

[shesez]

When I stop at lights and the delay is longer than 30-40 seconds the brake pedal starts to fade to th floor. I have to increase presure to stop the car moving forward. We have bled the brakes so no air locks. Wondering if it could be the brake booster or possibly a vacuum problem - the vacuum should be highest at idle

Any ideas

[aaronng]

The brake master cylinder might be leaking internally. Definitely get it checked out as it is a safety issue!