I've got two academic references on my CV, but it just struck me, that they know only of the work I did with them (not my home institution). Do I need an additional reference, who can state that what I say in the CV (about grades, qualifications etc) is true?

I wouldn't have thought that that would be necessary. You may be asked for evidence of your qualifications in the form of certificates though. You will certainly need to show your degree certificate at some point.

Hello Unknown,

If you have done a degree at a university (not your home uni), how do you expect someone from your home uni to verify what you have done at another uni? Does that make sense? If you have done a degree and they have awarded you a certificate it shouldn't matter. If you are having problems with referees just change them because in life you will always have unscrupulous, malicious people who will make it their point of duty to hinder you.

Well if they take you they will want to see the original qualification papers(the degree), so there's no need to prove that with a refree. A refree that you have worked with and who know you are probably better because they can judge your abilities a lot better that someone from the old uni who might not remember you ..