The press conference is due to get underway around 14.15 CET.
Rebel MP Anna Soubry has called on "one-nation Conservatives" and Liberal Democrats to join a breakaway group in the UK's parliament.
Conservatives Soubry, Sarah Wollaston and Heidi Allen quit Britain's ruling party on Wednesday citing Brexit among other reasons.
You can watch the trio's press conference in the video player, above.
They will join an independent group formed by eight former Labour Party MPs, who left the UK's main opposition earlier this week.
Soubry, who has often clashed with Theresa May's government over Brexit, supports another referendum on the issue.
Explaining her move to quit the Tories, she said it had been with a heavy heart.
"The truth is, the battle is over and the other side has won," said Soubry. "The right-wing, the hard-line anti-EU awkward squad that have destroyed every leader for the last 40 years are now running the Conservative Party from top to toe,"
Addressing what she called "one-nation Conservatives" and Liberal Democrats, Soubry said: "Come and join us."
'Running down the clock'
Another one of the rebel MPs, Sarah Wollaston, accused May of running down the clock on Brexit and said it was tantamount to backing a no-deal scenario.
The country is being pushed towards the "cliff-edge abyss", added another departing MP, Heidi Allen.
"We are putting our heads above the parapet and we might fail. But isn't the prize worth fighting for?" added Allen.
Local associations becoming 'blue-kip'
All three MPs talked about claims that local Conservative Party associations were being taken over by anti-EU activists.
The grassroots organisations were becoming 'blue-kip', said Soubry,
It was a reference to the traditional colour of the Conservative Party and an alleged shift to the right towards UKIP.
One of the results of this change had been that Conservatives like her, who challenged the government over Brexit, were being labelled traitors and threatened with deselection at a local level.