Labour and the Liberal Democrats appear to have made space for each other in byelections held in Conservative seats, spending figures acquired by the Guardian show.
The figures also show Labour lost the Uxbridge and South Ruislip byelection despite outspending the Conservatives by more than £21,000 in the campaign.
The release of the figures comes before two byelections later this week, in Tamworth and in Mid Bedfordshire.
The Mid Bedfordshire byelection is likely to mark an end to an apparent tacit agreement between Labour and the Liberal Democrats for one party to heavily contest Conservative-held seats, with both opposition parties claiming Nadine Dorries’s former constituency is theirs for the taking.
In June, Ed Davey, leader of the Liberal Democrats, ruled out a tactical voting pact with Labour ahead of byelections in Uxbridge and Mid Bedfordshire. He said: “There’ll be no pacts, no deals. We will fight both byelections. Voters will make the decision.
“They’ll decide which party is best placed to beat the Conservatives. We’ll put our case in both constituencies.”
But the spending figures for Uxbridge and South Ruislip suggest the case was not as strongly made to the potential Liberal Democrat voters in Boris Johnson’s former constituency as those in Somerton and Frome, where another byelection was held on the same day, 20 July.
In Uxbridge, Labour spent £96,785.74, coming close to the spending limit of £100,000. Danny Beales, the party’s candidate, narrowly came second, with 13,470 votes to the Conservatives’ 13,965 votes, securing the seat for Steve Tuckwell. The Tories spent £75,267.65, £21,000 less than Labour.
Meanwhile, the Liberal Democrats spent £6,021.15 on their candidate, who came in fifth place with less than 5% of the vote, forfeiting a £500 deposit.
But in Somerton and Frome, the spending was almost reversed: the Liberal Democrats spent £94,430.11, beating the Conservatives who spent £90,389.01. Labour, who came in fifth place behind the Greens and the Reform party, lost its deposit and spent only £7,486.90.
A Liberal Democrat source said: “One of the realities of first past the post is it incentivises every party to concentrate its resources on the seats they have the best chance of winning.
“You’ll see a huge variation between seats which are right up to the limit and as close as one can respectfully get to spending almost nothing. The expense return totals give you the real insight as to what a party thought its chances were in the seat.”
They added: “I think you will see a different pattern in the spending in [the Mid Bedfordshire] byelection. I think Labour are wasting their money, as you’d expect me to say. But Labour have been putting more effort in than some of the other previous contests in this parliament.”
A Labour spokesperson said the party was “investing in our campaign and spending to the legal limit”.
A third byelection was held on the same day in Selby and Ainsty in North Yorkshire, where Labour spent a similar amount as in Uxbridge but with greater success for its candidate, Keir Mather. The Conservatives, who spent £87,622.89, were again outspent by Labour’s £93,041.89. The Liberal Democrats, who came sixth and lost their deposit, spent only £7,549.88.
In Mid Bedfordshire, tension between Labour and the Liberal Democrats, with both fiercely contesting the seat, has bubbled over into accusations of false claims and dirty tricks.
A Conservative source described the byelection as a “phoney war” and said: “On the surface they’re tearing chunks out of each other, but behind the scenes the Liberals have stopped targeting Labour voters.”
