Should the spokes on my rear wheel be tighter on one side than the other ?

The non drove side spokes seem to flex more when you squeeze a pair together compared to the drive side ?

Is that correct or does my wheel need tensioning again.

Its correct.

Yep – drive side spokes are shorter/have a tighter bracing angle due to dish in the wheel, so will have to be tighter to keep the wheel in true.

One of the advantages of asymmetric rims is that they minimise this difference hence building a stronger wheel.

Renton,

Here is a pretty graph from the guys at skunkworksbikes.com showing the different tensions in a rear wheel from left side to right side.

As explained above it is perfectly normal.