Senate Question

Raise taxes to 75%. You'll lose the next election, then you can go to war.

Seriously, though, if you get your morale up near 100%, even the Pacifists won't overrule a decision to go to war.

Are you playing as the Pacifist party? If not, all you have to do is retake the senate by raising your morale for the next election. If you are the Pacifists, I would take AmulekBird's advice.

Please can you give me some pointers as to how fastest to raise morale?
Many Thanks

How to raise morale: Build improvements like Soil Enhancement, Habitat Improvement, Entertainment Network, Multimedia Center, Harmony Generator, Stadium, Teleporters. These will definately raise morale.
Lower taxes. Approval will go up, and approval is the same as morale.
Reduce pop on planets with overtly large pop numbers, i.e. Colony Ship. *WARNING* last ditch technique.

These will also cost money. Make sure you need them.