Xjyuk

Could the conundrum which faces the Government be overcome with support for a bill from the SNP?

It is well known that under the Fixed Term Parliaments Act, a motion for a general election requires the votes of two-thirds of MPs. However an alternative system has been mooted involving a bill requiring a simple majority, but one which is amendable, requires a fixed date, and has to pass through both Commons and Lords.

As things stand at present the Government may not be able even to get a simple majority based on Conservative votes alone. However the SNP, it is suggested may be prepared to support it.

Now let's suppose that the SNP amend it to provide for a new referendum on Scottish independence, the Government may be tempted to accept the arrangement. For it seems that it could be the only way that Boris Johnson could get an election prior to 19 October.

Would this be a valid parliamentary procedure?

They can certainly try, yes.

As with any other bill, they can table any amendments they like. Not all of them would be selected by the Deputy Speaker for debates or votes, though, and there is no guarantee that this one would.

Mechanically it might work, although there may not be enough time available due to prorogation, and the government has lost control of the order paper.

Politically it's nuts; it's an outcome the Conservative and Unionist party is extremely keen to avoid. It might result in enough defectors from the Conservative side of the vote to fail entirely.

There's an argument that starting with a bill whose sole purpose is to trigger an election, and then amending it to allow a Scottish independence referendum, would not be in order, as the latter is outside the scope of the bill.

Erskine May has this to say on the matter:

Any amendment (or new clause or new schedule) proposed to a bill must be within its scope. The scope of a bill represents the reasonable limits of its collective purposes, as defined by its existing clauses and schedules. In particular cases, difficult questions of judgment may arise.

However:

The scope of a bill may change in the course of the bill's passage through the House depending on the amendments made to the bill.

But even this has limitations. When a bill is sent to a committee for its consideration, the House can instruct the committee "either to empower it to do something which it could not otherwise do, or to define the course of action which it must follow".

However, such instructions still have limitations. In particular:

Instructions are out of order if they attempt to embody in a bill principles that are foreign or not cognate to it; if their objects are inconsistent with the decision of the House on second reading

So it's possible that any attempt to instruct the committee to widen the scope of a bill as described above may be ruled out of order by the Speaker; and hence any related amendment would similarly be ruled as out of order.

However, this is very much at the discretion of the Speaker and committee chair, so it's also possible that this could, in theory, happen.

(See also the section on inadmissible amendments.)