When was the last time a government bill was defeated at its second reading in the Commons?

The government is hoping a series of concessions will be enough to push through its Universal Credit and Personal Independence Payment Bill, which has its second reading in the House of Commons this afternoon.

With a current working majority of 165, Labour’s bills would usually expect to be granted safe passage by a comfortable margin, but dozens of the party’s MPs are reportedly threatening to rebel, making the future of the legislation less certain.

Before it can become law, a public bill must generally pass through five steps in both Houses of Parliament—first reading, second reading, committee stage, report stage and third reading.

Bills are not opposed at first reading, as this is usually a purely formal event, without any actual debate or voting. The second reading, however, is where bills can be opposed if MPs put forward “reasoned amendments” to the legislation, or vote against the motion to give the bill its second reading. This is the earliest opportunity MPs have to get a bill thrown out.

If a bill is defeated at second reading, it cannot be re-introduced until the following parliamentary session, meaning the proposed reforms would likely have to wait until at least next year.

At one point more than 120 Labour MPs had threatened to vote against the government’s welfare legislation, forcing a U-turn and the introduction of multiple concessions. It is unclear whether these will be enough to ensure the bill’s passage, as earlier this morning it emerged that at least 39 Labour MPs still intend to oppose the legislation.

Defeating a government bill at second reading is extremely rare—according to the Institute for Government, the last time that happened was in 1986. This was when Margaret Thatcher—who had a Commons majority of 144— failed in her attempt to reform Sunday trading laws.

Governments more commonly experience defeats on amendments to bills, or on other parliamentary motions—particularly in the House of Lords, where governments do not enjoy an in-built majority of their own party members.