Agree: it does appear that the current system can end up being in effect, a deceptive fraud on the electorate. They promise one thing and then do whatever they want. The manifesto should be an enforceable mandate of what they must deliver.
Strongly related to this issue is a point I made on the anti-democratic excesses and of the Party Whips. See on this link https://forum.policyplatform.co.uk/t/starmer-treaties-future-treaties-act/1281/8?u=charliebravo
