Theresa May must not be allowed to lead the Conservatives into a snap election, senior Tories have warned.

A series of ministers and MPs have told The Telegraph the party would be “annihilated” at the polls if the Prime Minister insisted on fighting a campaign to face down Parliament over Brexit in the coming months.

The warning came as it emerged that senior ministers have virtually given up any hope of the Democratic Unionist Party, which is propping up the Government, supporting Mrs May’s Brexit deal.

Its MPs’ refusal to budge means she faces a growing likelihood that Parliament will legislate this week to force her into seeking a soft Brexit, if backbenchers can agree on a specific plan. Separately, current and former ministers were rapidly stepping up preparations for a leadership contest after Mrs May pledged to stand down after Brexit.

Matthew Elliott, the former chief executive of the official Leave campaign, has begun advising Sajid Javid, the Home Secretary, while allies of other candidates were gathering support.

But with MPs lining up to oppose her deal again next week and backbenchers insisting they will not allow a no-deal Brexit, Mrs May’s departure date was unclear.

Amid warnings that a no-deal exit could still take place “by accident” next month, Whitehall sources said that planning by departments including the Home Office and Environment department was at “full tilt”.