I agree there is probably no great appetite in Labour for an election right now. Of course there isn’t. Parties usually want to hang on. But “they were voted in for five years” is not quite right. They were given a maximum Parliament, not a guaranteed five-year tenancy. General elections can be called early, and historically they often are when a PM wants legitimacy, authority, or a reset.
Eden became PM in 1955 and called an election almost immediately to secure his own mandate. Wilson went early in 1966 to turn a tiny majority into a workable one. Heath went early in February 1974 asking “Who governs Britain?” Wilson went again in October 1974 to get a better mandate. May went early in 2017 after taking over from Cameron because she wanted her own Brexit mandate. Johnson went early in 2019 to break the deadlock and get authority for his programme.
So no, it would not be constitutionally required. But politically, I think they probably will have to do it once they get a new leader. After a terrible local election result for the incumbent government, replacing the PM and then just carrying on as if nothing has happened would leave them with almost no legitimacy at all.
A new leader would be trying to say “this is a new government, with a new programme, and a new direction.” At that point they need the country’s permission, not just the permission of Labour MPs and party members. Otherwise it looks like an internal party stitch-up to keep hold of power.
The danger for Labour is that staying put can look less like responsible government and more like squatting in office until eviction day. Brown and Sunak both suffered from that problem. They were legally entitled to govern, but politically they never fully escaped the lack-of-mandate charge.
So I am not saying Labour would want an election. They obviously wouldn’t. But if Starmer goes after such a brutal rejection at the polls, I think the next leader may have very little choice. Sometimes going early is not wishful thinking. It is damage limitation. Staying when the public has clearly turned against you can poison the party brand for years.