This depends on what the specifics of the situation are. There are some cases, as with diplomatic negotiations, where it is better for parties and governments to withhold the truth. But there are other cases, as with how much money government is spending, where secrecy is not acceptable.
For example, right now in the US, Republicans and Democrats on a "supercommittee" are supposed to be negotiating ways to reduce the US deficit. They want to do this in secret and I approve. As long as they present the true deal they have made to the people before Congress votes on it, it is good for them to operate in secret so they can make hard decisions without being pressured. I am not saying we should allow the whole process to be secret, but it is fine if the negotiations are secret and we are allowed input about whether to accept the final product.
So I don't think we need to be told the truth about every step of political processes. But we do need to be told the truth before we (or our legislators) get to vote on proposals.
Do you think you could elaborate if you were looking at it in a morally ethical way for lying?