It is said that the personnel of the Departure Department of the European Union played an important role in the possible actions that the Prime Minister will undertake in a scenario of "war games", according to The Sunday Times.
Brexiteers Boris Johnson and Jacob Ree-Mogg were included in the war game, as well as James McGrory, the popular vote director.
A source told the newspaper: "Public officials have to prepare for each eventuality and with the ability of the Prime Minister to command the support of Parliament that seems more unstable each day, his job is to make contingency plans for each possibility, even remotely , even a second referendum. "
It comes a day after 670,000 people took to the streets of London to march towards the so-called "Popular Vote".
The campaign is putting pressure on parliamentarians after months of street rallies.
But The Sunday Times added that up to 50 conservative parliamentarians, including five frontbenchers, are "accessible."
A spokesman for Downing Street said: "The prime minister has been clear, there will be no second referendum, we had a popular vote in 2016.
"A second referendum would really be a vote of politicians, politicians who tell people that they were wrong the first time and that they should try again." That would do a lasting damage to faith in democracy. "
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Update of 9.45 a.m. The United Kingdom could accept a longer Brexit transition if the EU eliminates the backup plan
Britain would accept a possible extension to its post-Brexit transition period with the European Union if the bloc eliminates its demand for Irish support, said Brexit's British minister, Suella Braverman.
The talks between Britain and the EU have been stalled by a disagreement over the backing: an insurance policy to ensure that there will be no return to a hard border on the island of Ireland if a future commercial relationship is not made on time.
She told Sky News: "We would accept a possible extension in a few months, either a finite time limit or a mechanism to free ourselves from it if that meant breaking this deadlock and avoiding the very unattractive proposal of the EU, which It is an indefinite term: customs union and a period of limbo. "