Johnson's majority down to one after by-election
Boris Johnson has been left with a working majority of only one in the House of Commons after the Tories were defeated in the Brecon and Radnorshire by-election.
The Liberal Democrats won the mid-Wales constituency by a margin of 1,425, swinging the vote nearly 12pc from the Tories.
An electoral pact saw Plaid Cymru and the Green Party stand aside to boost the chances of a pro-EU MP being elected, and Lib Dem leader Jo Swinson predicted further alliances in future.
The first electoral test of Mr Johnson as Tory leader became his first defeat with Jane Dodds's victory.
The Tory loss will add to the prime minister's challenges to steer Brexit through parliament and may increase the chances of a snap general election.
With the vote coming eight days after Mr Johnson was installed, it is the quickest by-election defeat for any prime minister of the post-War period.
It also led to calls from senior Brexiteers for the Tories to consider a pact with the Brexit Party to stave off further deals among Remain parties.
However, a government spokesman said the prime minister had "no plans at all" to make a deal with the Brexit Party, and "absolutely no intention" for any coalition with Nigel Farage.
Appearing alongside her new MP, Ms Swinson said: "I will fight to keep our country in the European Union, and we now have in parliament one more MP who will fight to make that happen."
The Lib Dem leader said she exchanged messages with the Green and Plaid leaderships and said: "I think there will be more co-operation in future."
Welsh Lib Dem leader Ms Dodds said: "My very first act as your MP when I arrive in Westminster will be to find Mr Boris Johnson wherever he is hiding and tell him loud and clear: 'Stop playing with the future of our communities and rule out a no-deal Brexit now'."