David Deans,Wales political reporter,
Gareth Lewis,Wales political editorand
Elliw Gwawr,Wales political correspondent
Welsh Labour spent twice as much as eventual winners Plaid Cymru during campaigning for the Caerphilly by-election, documents seen by BBC Wales show.
First Minister Eluned Morgan’s Labour spent £98,447.19 trying to avoid the party’s first parliamentary defeat in the seat for more than 100 years, only to come in third place.
Plaid’s candidate Lindsay Whittle was victorious after his party spent £46,933, while Reform UK, which came second, spent £96,125.
Labour said: “All necessary declarations have been made transparently and in full accordance with the rules.”
The Senedd by-election on 23 October was triggered by the death of Labour MS Hefin David.
Political parties are required by law to file returns detailing what they spend during by-election campaigns, which can be viewed by the public.
Labour spent £26.51 per vote if their total was broken down by the 3,713 votes for the party’s candidate Richard Tunnicliffe.
The party’s return lists advertising spend worth £40,470 and unsolicited material like leaflets to electors worth £45,840.
The party paid for £31,295 of advertising on Meta and Google.
Labour provided receipts for six Airbnb bookings for 22 people stretching from September into October last year, worth a total of £25,315.
The properties were located in Trefforest, Blaenau Gwent, Cardiff, Hirwaun, and two in Newport.
The value of the bookings differed from the figure written in the return, however, which declared a much smaller sum of £3,321 for “staff accommodation” from Airbnb.
When BBC Wales asked Labour to explain the difference, it was told it was common practice for candidates and parties to divide and share spending where some elements of an invoice count as regulated expenditure and others do not.
Welsh Labour was asked if they were staff from the UK party but it did not answer the question.
Reform’s return was divided into £55,239 for unsolicited material to electors, £16,500 for staffing and accommodation, £16,003 for advertising, admin costs of £6,744, and £1,637 for transport.
Individual entries in the return show Reform spent £49,854 on leaflets and letters, including one entry for a letter that was worth £17,084.
Reform’s unsolicited material category included £4,794 in spending on Facebook.
Plaid Cymru spent £46,933 according to its return, including £21,649 on unsolicited material to electors, £12,794 on advertising, £6,710 on agent and staff costs and £5,208 on accommodation and administration.
A Plaid spokesperson said it was “proud of the positive, people-powered campaign we ran, with volunteers knocking doors and delivering leaflets in every corner of Caerphilly”.
Reform was also asked to comment.