Sir Keir Starmer on Wednesday declined to rule out an electoral pact with the Liberal Democrats.
The Labour leader had used his conference speech on Tuesday to say there would be “no deal under any circumstances” with the SNP – but there was no mention of any ban on deals with Sir Ed Davey’s party.
Asked to rule out a deal with the Lib Dems, Sir Keir told GB News: “We’re going for a Labour majority – I’ve been very clear about that – and I was very clear that we wouldn’t do a deal with the SNP.
“If you look at the challenges we face as a country, then I do not believe putting a border between England and Scotland is going to help us address those central challenges.”
Some in the Labour Party have urged Sir Keir to sign a formal non-aggression pact with the Lib Dems, with candidates standing aside to allow those best placed to beat the Conservatives in their seat to do so.
The Labour leader is unlikely to go so far, but observers believe unofficial arrangements could be made in key constituencies. In June, there were suspicions that the parties worked together to secure a gain in Wakefield for Labour and one for the Lib Dems in Tiverton.
Sir Keir is much keener to rule out any pact with the SNP because it could be used by the Tories, as in past elections, to warn of a “coalition of chaos” that could put the Union at risk.
If Labour did have to be propped up by the SNP, it would be likely they would have to agree to another Scottish independence referendum.
In his conference speech, Sir Keir said: “Scotland needs a Labour government that can deliver change. But it also needs the power and resources to shape its own future, whoever’s in power in Westminster. And the SNP are not interested in this.
“For them, Scotland’s success in the UK is met with gritted teeth, seen as a roadblock to independence, and so they stand in the way. We can’t work with them. We won’t work with them. No deal under any circumstances.”
A spokesman for the Labour leader said on Tuesday that he had only mentioned the SNP in his speech, and not the Lib Dems, because it was a section about Scottish politics. The spokesman said Labour was going for a majority at the next election without help from any party.