Political deals used to be done in smoke-filled rooms, but parliamentary plotting nowadays happens mostly on WhatsApp.

On Sunday night, a message sent by Boris Johnson to a private WhatsApp chat group for Tory MPs were “leaked” to the media. However the text, professing support for Theresa May, also looked very much like it was intended to be leaked. Politicians know by now which of their WhatsApp groups are a circle of trust and which ones have political foes lurking within.

The foreign secretary’s message to a closed group of MPs on the encrypted app was apparently sent on Sunday morning, following speculation that he was preparing to launch a leadership challenge. His message listed eight reasons why he would be backing the prime minister, with supportive replies from MPs Michael Gove and Conor Burns.

WhatsApp has quickly become the medium of choice for MPs to organise and agree lines to take in response to breaking news. When politicians suddenly appear on television repeating much the same lines as each other, you can take a guess that something has been agreed upon among WhatsApp messages between colleagues.

Journalists noted the rapidness of how quickly Tory MPs went from privately expressing shock at George Osborne’s appointment as editor of the Evening Standard to publicly declaring support for him to stay as an MP. That line was agreed by friends of Osborne on WhatsApp.

One of the most influential WhatsApp groups in parliament is the European Reform Group coordinated by Tory MP Steve Baker for around 60 of the party’s most Eurosceptic MPs, including Dominic Raab, Michael Gove, Suella Fernandes and Iain Duncan Smith.

Coordinated attacks organised via the group include piling pressure on Mark Carney, the governor of the Bank of England, who was challenged repeatedly on the airwaves and on Twitter by members of the group because of the bank’s predictions about the economic consequences of Brexit.

By and large, the group is supportive of May’s premiership – for now.

Labour has its own organising WhatsApp groups, including official channels for whips to get messages quickly to MPs. It also has a group for all female Labour MPs, the platform for several spats during last summer’s leadership election.

Labour MP Lucy Powell once had to apologise after accidentally sending a critical WhatsApp message about shadow education secretary Angela Rayner to the entire women’s parliamentary Labour party rather than a group for moderates. Powell apologised profusely for “being a cow”. Will whoever “leaked” Boris’s message do the same?