Another day, another campaign appears to have fallen foul of the UK’s election spending rules. The Electoral Commission is investigating the left-wing membership network Momentum’s outgoings during the general election.

Momentum – which backs Jeremy Corbyn’s leadership of the Labour party – may have spent over the limits for a non-party campaigner. Such organisations are allowed to target spending for a particular party or candidate within a limit in each of the devolved nations (£31,980 in England, £3,540 in Scotland, £2,400 in Wales, and £1,080 in Northern Ireland, totalling £39,000).

To exceed this, they have to be authorised by said party. Momentum filed below the permitted spending limit for an unauthorised registered non-party campaign group: £38,743.

The Electoral Commission is investigating whether the group exceeded this limit, and submitted inaccurate returns.

Momentum has admitted administrative mistakes in a statement:

NEW: Momentum admits 'administrative errors' over its election spending after watchdog probe opens pic.twitter.com/lL6jIkTTit — Dan Bloom (@danbloom1) December 7, 2017

As I’ve written before, during the Tories’ election fraud scandal following the 2015 election (which also involved other parties), the spending rules are outdated. They enforce a rather meaningless divide between national and local campaigning during a general election, while failing to take into account micro-targeting on Facebook and other digital platforms.

So unknowingly breaking the rules is fairly common, and in the eyes of most parties points not to wrongdoing but to a system desperately in need of change. This is true of Momentum too, which does a lot of its most effective campaigning online.

It’s also important to note how few resources Momentum has. It only had a handful of paid staff over the election period – the majority were volunteers – and overall it spent £2,000 on Facebook advertising. The legal spending limit for Momentum in each constituency would have been £60, and going by its total expenditure filed to the Electoral Commission, it spent £59.60 in each seat.

Compare this to the figures for which the Electoral Commission is investigating Vote Leave (potentially exceeding a £7m spending limit), Arron Banks (£6m of loans to Leave.EU) and Leave.EU (£2.3m of donations to campaigners), and you learn more about Momentum’s remarkable success than its alleged errors.

NB. The 0.57 per cent in the headline assumes the official Leave campaign spent its declared £6,789,892 and Momentum spent its declared £38,743. Both groups are under investigation, so it may turn out that they went over their spending limits.