Senior Labour MPs appalled by Jeremy Corbyn’s performance over the Salisbury poisoning have been in secret talks with the Liberal Democrats and at least one Conservative MP about forming a new political party called Start Again.

Plans for a new pro-European centre party have been openly discussed as part of cross-party discussions on Brexit, according to sources present.

One of those involved in the plotting — a former member of the shadow cabinet — told The Sunday Times that Corbyn’s refusal to blame Russia for the attack would cause MPs to abandon Labour. “This is a watershed moment,” the MP said. “It has caused a number of people to question why we are in this party.”

Sources say a number of possible names — including