What is a private member's bill, and do any become law?
A bill introduced by an MP or peer who is not a government minister — and a small number do become law, though the mechanisms that allow it are narrow and easily obstructed.
The three routes in the Commons:
The ballot. At the start of a session, MPs enter a ballot and twenty names are drawn. Ballot bills get priority on the limited Friday sitting days allocated to private members' business, and the highest-placed have the best prospects. These are the bills with a realistic chance, and successful MPs are immediately approached by campaign groups and government departments with bills ready to go.
Ten minute rule. An MP makes a short speech introducing a bill. Almost never becomes law, and functions as a way of raising an issue and testing opinion.
Presentation. A bill is formally introduced without a speech, and rarely progresses.
Why most fail. Not through rejection but through lack of time:
Limited sitting days. Only a small number of Fridays are available, and bills are taken in order — so a bill low in the queue may never be debated at all.
Filibustering. A bill must complete its second reading debate to progress. An opponent speaking at length until time expires prevents this, and the tactic is used openly. A closure motion can end debate, but requires a minimum number of MPs present to vote for it — and getting a hundred MPs to attend on a Friday, when most are in their constituencies, is the practical obstacle that kills most bills.
Government opposition. Without at least government neutrality and drafting assistance, a bill will not survive the process.
What succeeds. Bills that are narrow, technically competent, uncontroversial, and — decisively — not opposed by the government. Governments sometimes use the route deliberately for measures they support but do not wish to sponsor, particularly on matters of conscience.
The significant examples. Several of the most consequential social reforms of the twentieth century were private members' bills, including the decriminalisation of homosexual acts, the abolition of the death penalty and the Abortion Act — all facilitated by government granting time.
Handout bills are those supplied by departments to successful ballot MPs.
In the Lords, the procedure differs and bills more readily pass that House, then struggle for Commons time.
General information about UK parliamentary procedure.