Facts not opinions
Civil servants should be allowed to talk to anyone if all they are doing is offering facts: e.g. "How many unemployed are there this week?" or "What did the minister say last week?"
Civil Servants should not, however, provide opinion.e g. "Is the unemployment rate too high?"
Now, I accept, that it can sometimes be that the lines between fact and opinion can be a little grey, but you get the idea.
Ministers should NOT be involved in handling facts. They'll only distort them.