The three former Tories had cited Brexit and Theresa May's handling of the negotiations with the EU as the impetus for them leaving the government.
Their defection and the new party's presence in the Commons was curiously not acknowledged during Wednesday's PMQs by the prime minister or Jeremy Corbyn.
However, David Cameron did step into the debate and their decision to leave the Tories, which is something he profoundly disagreed with.
In a tweet, he wrote:
I am sad that three Tory MPs have left the party. I back the open primaries that saw two of them elected and supported them all.
I respect their decision, but disagree with them: we need strong voices at every level of the party calling for the Modern, Compassionate, Conservatism that saw the Conservative Party return to office.
Our party has long been able to contain different views on Europe. Everyone must ensure that can continue to be the case.
Sad that three talented Tory MPs have left the party… I respect their decision, but disagree with them. https://t.co/YwkHVvB82d