We need to stop disinformation in UK political adverts. Here’s a chance to do so | Letter

Andy Burnham’s comments about Russian interference in Brexit (Report, 11 October) and the warning by the MI5 chief, Ken McCallum, against exaggerating its impact (Report, 13 October) risk overlooking another serious threat to electoral integrity: disinformation from our own political parties and campaigners.

Foreign interference deserves scrutiny, but misleading factual claims in electoral advertising are unregulated, unlike in commercial advertising. We have four sets of rules to ensure an advert for a packet of sausages is accurate, but none for the most important advertising of all – ads that influence how we vote.

With our fragmented five-party politics producing increasingly close elections, misleading advertising can be decisive. Brexit was decided by a 51.9%-48.1% vote split. Our research into May’s local elections found that 41.4% of wards in England were won by margins of less than 5%, with nine decided by a single vote.

We also identified misleading electoral advertising in some of the closest contests. Regulating factual claims in electoral advertising was a key recommendation of the House of Lords select committee on democracy and digital technologies in 2020. The representation of the people bill, currently going through parliament, offers an opportunity to act.

An amendment covering the same scope attracted 37 MPs as sponsors in the Commons, and we are working with peers in the Lords to take it forward. Burnham signed up to our voluntary code for honest electoral advertising in 2024, which forms part of the proposed amendments.

We should tackle foreign interference, but we can’t continue to ignore the disinformation put out by our own political parties. Alex Tait Reform Political Advertising • The head of MI5 confirming that Russia did try to interfere in the Brexit referendum is highly significant to the result.

The vote share achieved by the leave campaign was 51.9%, as against 48.1% for the remainers. This was a majority of just 3.8%. If Russian interference swayed just 2% of voting intentions, this would erode the much-vaunted majority of the leave group, and remainers would emerge as victors.

MI5 should carry out an impact assessment of Russian interference using the most up-to-date AI, and attempt to quantify shifts in voting patterns. This would go a long way towards introducing a new referendum. Dr Joseph Mullen Former senior lecturer, University of Manchester • Have an opinion on anything you’ve read in the Guardian today?

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