Jeremy Corbyn has spoken of his “regret” after seven MPs quit the party citing his approach to Brexit and the handling of anti-Semitism within Labour.
Chuka Umunna and six others quit the party at a dramatic press conference on Monday to sit as Independents.
In his first formal appearance since the split, Mr Corbyn thanked the MPs for their work but suggested they now needed to consider calling by-elections and testing their decision with voters.
The Labour leader, addressing the Make UK conference in London, said: “I regret that seven MPs decided they would no longer remain part of the Labour party, I thank them for their work.
“I hope they recognise that they were elected to parliament on a manifesto that was based around investment in the future, was based around a more equal and fairer society and based around social justice.”
The comments came as rumours swirled around Westminster that as many as 30 more MPs could follow the group and sit as Independents.
One Scottish Labour source told the Press and Journal: “Jeremy needs to listen to the concerns otherwise he will have a number of other MPs leaving.
“The words from Tom Watson were encouraging, I just hope there’s a realisation now that things need to change.”
Aberdeen City Council co-leader Jenny Laing said she was “disappointed” that the seven MPs had made the decision to leave.
She said: “I have been a member of the Labour party for a long time, I believe in Labour values and I believe Labour is the best way to deliver positive change for people in Aberdeen and more broadly.
“I am disappointed when I see people moving away from that.”
Ms Laing, who is currently suspended from the party for striking a power-sharing deal with the local Conservative group, said she feared the decision could “damage” the prospect of a Labour government.
She said: “We have seen in the past that setbacks like this can cause damage, we now need to come together because a Labour government is the best thing for Aberdeen and the UK.”
Westminster is also awash with rumours that some Tory MPs could throw in their lot with the breakaway group.
One Scottish Tory source told the Press and Journal that two backbenchers could cross the floor, they said: “There’s talk of Sarah Wollaston and Heidi Allen leaving, it’s not a surprise, they have always been more social democrat than Conservative.”