"absolutely confirm that there is no intention in forthcoming legislation either to weaken encryption or provide back doors."
If we must have monolithic parties, they should provide diffs of any changes to legislation they wish to enact as part of their manifesto. When a party is then elected, only those changes can be committed to legislation. At least the people get a say on the laws that they will have to live under and can in effect veto any significant changes.
It will put an end to Govs coming in and doing whatever the fsck they want once elected, usually defending their actions with "well you elected us".
Or something like that... I haven't worked out the details.