There has been new allegations of "breaching of rules" by some pro-Brexit groups in the Brexit referendum. This new allegations join previous ones that electoral laws have been broken (also here). Some have called the result "illegitimate"; others "invalid".

Now, legally, in the UK, when can a referendum result be officially pronounced as invalid, in the sense that it result is not binding, and must be rerun?

If this is never the case, then there is all the incentive for parties to cheat. In my view, the legitimacy of democracy itself is in question if cheating in a democratic process cannot invalidate it, and its only consequence is financial penalties to the cheater. Thus, I imagine there must be a rule which puts a limit to this incentive.

In the UK, there exists the Electoral Commission, which rules regarding referendums include "certifying and announcing the result." Surely certification must be based on some definition of legality of activities of parties involved?

PS: there is this related thread, which is about what happens if rules are broken. My question is a bit broader, asking if there is any way in which an official organisation like the Electoral Commission has the authority to qualify a referendum result as "invalid".

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    Note that the Brexit referendum actually never was binding, so a proof of cheating would not change anything legally. British parties chose to adhere to the referendum result, they did not have to.
    – Thern
    Commented Jul 17, 2018 at 11:02
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    I have added some info at my answer explaining the political points against invalidating/rejecting the results of the Brexit referendum (then again, there would not even be a need to invalidate the results to cancel Brexit because the referendum was not binding)
    – SJuan76
    Commented Jul 17, 2018 at 11:18
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    I've edited your question to be clearly about the UK, because legislation is going to vary widely across the globe... Commented Jul 17, 2018 at 11:25

1 Answer 1


A referendum is never binding.

It never has to be re-run.

A bill creating a referendum may have clauses that are intended to make the result binding. An example of which was the AV referendum, in which a condition of the bill, as introduced by the coalition, was to make the result binding. The reason for this was that the major party in the coalition was opposed to AV and the minor party feared that even if the referendum came in favour of AV, the major party would simply ignore the result.

However, no referendum, vote of parliament or judicial ruling can prevent a future parliament from passing any bill or motion it chooses. A future parliament can pass a bill that repeals the binding nature of a previous referendum bill.

Similarly, there are no conditions under which Parliament has to hold a new referendum. However a new act of Parliament may be required if a Judge orders an election void and orders a new vote.

In the UK, the process of challenging an election result is called an "electoral petition". These are held before a judge and require that

corrupt or illegal practices were committed by a candidate or his or her agent or ‘such practices so extensively prevailed in an election that they may reasonably be supposed to have affected the result’; (source Electoral Commission)

In other words, the judge must be convinced that, not only did one side cheat, but that cheating clearly affected the outcome. That is a high bar to reach. The Electoral Commission does not decide on petitions, only a Judge.

Petitions must also normally be brought within 21 days of the result. (subject to some exceptions)

The consequence of this is that even while Vote Leave have been fined and censured, this would not lead to a second referendum.

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