MPs in the new Independent Group have appointed a convener as they held their first meeting after dramatically breaking away from their former parties last week.
Eight Labour MPs were followed by three Tories in quitting their parties to form a new centrist grouping in potentially the most significant realignment in British politics in a generation.
At their first formal meeting as a group on Monday afternoon, they unanimously appointed former Labour MP Gavin Shuker as convener, but did not elected a leader.
Speaking after the meeting, the group said it had discussed its values and priorities, but former Conservative Anna Soubry said the most important priority was Brexit.
The Broxtowe MP added that the group of 11 parliamentarians will be supporting the Cooper-Letwin amendment this week.
She said: “The most important thing this week is Brexit.
“We know we have the Cooper-Letwin amendment, I don’t think there’s any doubt about the fact we will be supporting it.”
Mr Shuker said Parliamentary business was the “most important thing we can be doing”.
And Heidi Allen said: “We have just had a really good first meeting, discussing a lot of things structural around process, values and priorities.
“We have elected Gavin (Shuker) as convener. That was a unanimous choice.”
Ex-Labour member Chuka Umunna insisted at the weekend that they were not yet a party or a movement, with a fully worked out programme for government, but simply a group of independent MPs.
Members have said they are united by a shared “non-tribal” belief in “progressive” values combined with deep unhappiness at the directions their former parties had taken, particularly on Brexit.
Among the ex-Labour MPs there was also anger at what they said was the failure of the party leadership to deal with the spread of anti-Semitism in the party.
However they are likely to face pressure to move quickly to formally establish themselves as a party – with reports that some former Labour backers are ready to help bankroll them.
Mr Umunna, a former shadow minister, played down reports that he was favourite to be the first leader, although he acknowledged that he wanted to play the “biggest role” in the group.
Liberal Democrat deputy leader Jo Swinson said she was expecting to meet with the new group later this week, having spoken with some of its members in recent days.
Ms Swinson said the Lib Dems were ready to “work with” the new grouping, though she played down suggestions of a formal pact between the parties, insisting she had no fixed blueprint for how they should co-operate.
“I think we need to be working together with the Independent Group MPs but we need to find a 2019 way of doing that and I’m open-minded about how that looks,” Ms Swinson told BBC Radio 4’s Today programme.
“I want to approach this with a very very open mind, potentially to have radical change.
“It is not very often we get a moment to break up the broken political system and we have that moment now.”
Asked if that could include Lib Dems agreeing not to stand candidates against the 11 TIG MPs, Ms Swinson said: “I don’t think we should be taking any of these things off the table.”
She added: “I will welcome anyone to the Liberal Democrats who shares my liberal values, and obviously I want more people to join the Lib Dems.
“But I am not going to be petty about this and suggest that I am not going to work with somebody who shares many of my values just because for whatever reason they don’t feel that they can join my party.”