On 14 February, peers passed the Parliamentary Voting System and Constituencies Bill at third reading. The bill received Royal Assent on 16 February.
The bill paves the way for a referendum on changing the Westminster voting system from first-past-the-post to the alternative vote (AV), whereby voters rank candidates in order of preference.
Also included in the bill are plans to reduce the number of MPs by 50 and to redraw the constituency boundaries so that the number of electors is spread more evenly across parliamentary seats.
Why did the bill take so long to progress through the Lords?
Labour opposed proposals for boundary changes and objected to plans to cut the number of MPs being included in the same bill as the referendum plan.
Labour urged the government to split the bill into two parts,
allowing the AV part to be passed, leaving the House more time to scrutinise the other proposals in detail.
The Electoral Commission warned that the bill had to become law by mid-February or
the referendum would be delayed.
The bill was eventually passed in time for the referendum on 5 May.
What was the government's position?
The government refused to split the bill into two parts - AV and boundary reform were issues linked by the parties as part of the coalition negotiations, and splitting them up could cause internal wranglings in the coalition.
Electoral change and boundary reform are individual priorities for the Lib Dems and the Conservatives respectively.
The government said enough time was set aside for proper scrutiny of the bill had Labour not engaged in "filibustering" tactics to derail the coalition's plans.
Labour denies these accusations.
The bill's progress through the Lords was fraught with difficulty for the government, as the committee stage stretched from an original plan of five days to 17 in total.
In all, the government was defeated five times: over the date of the referendum; over keeping the Isle of Wight as one, complete constituency; over an amendment making the result of the referendum non-binding if less than 40% of the electorate vote and over the degree to which constituencies can vary from the electoral quota in exceptional circumstances. The fifth defeat was during ping pong when the Lords insisted on their amendment on the 40% threshold.
Deadlock was broken when three compromises were brought forward by the government: on public hearings (instead of local inquiries), on the Isle of Wight, and on a post-legislative review of the number of MPs.
However, the government did not bring forward compromises on variance from the electoral quota and a threshold for the AV referendum.
An attempt at a compromise by crossbencher Lord Pannick over the average size of constituencies was not insisted upon by peers during ping pong.
And Lord Rooker's amendment to make the referendum result non-binding if less than 40% of those eligible voted, was supported by the Lords during report stage, insisted upon during the first round of ping pong, but dropped in the second round.
The Lords passed the bill at third reading on 14 February. On 15 February, the Commons considered Lords' amendments. Then the Lords considered Commons' amendments on 16 February. Royal Assent was received on the same day.