Amid reports that Eurosceptics are also anxious that Mrs May was being bounced into a "soft Brexit" by civil servants as she lacks authority, a Number 10 source said: "The PM triggered Article 50, she set direction of the Brexit negotiations in her Lancaster House and Florence speeches and personally secured the deal that led to sufficient progress".
Shadow Brexit secretary Sir Keir Starmer said: "Five months after Labour set out the terms for strong transitional arrangements, David Davis appears to have finally woken up to reality".
Mr Rees-Mogg insisted the PM has his "full support" and said Mr Hammond appeared to be "obstructing Brexit".
A Downing Street source said: 'The Government's policy is that we are leaving the single market and the customs union.
The government's tone on Brexit needs to fundamentally change. "If [Brexit's opportunities are] taken off the table then Brexit becomes only a damage limitation exercise", he is set to say.
People who objected to his approach were disrespecting the thinking behind British voters' June 2016 decision to leave the EU, Hammond said. They did not vote for the management of decline.
"But it does come with the proviso that the United Kingdom needs to recognise that if it wants access to the European Union, to our market of 450 million and everything that goes with it, there are responsibilities, costs and obligations as well", Varadkar told reporters.
Jacob Rees-Mogg is the chairman of the influential European Research Group of backbench Tory Brexiteers.
He will talk about the transition - another source of anxiety to the pro-Brexit camp, who worry that the grace period created to help business risks prolonging indefinitely European Union membership in all but name. Accusing the Government of allowing itself to be intimidated by Brussels, the parliamentarian had stressed that he would not accept a model that would keep Britain in a system similar to the single market and customs union.
However, Davis may also repeat his exhortation to hardline Brexit supporters in Britain to ease off on criticism of the fact that the country will remain bound by essentially all European Union rules, including on immigration and the supremacy of European Union courts, for almost two years after Brexit.
"For the first time in more than 40 years, we will be able to step out and sign new trade deals with old friends, and new allies around the globe".
"I would expect it before the end of March", Davis told a parliamentary committee when asked when the terms of the transition deal would be agreed.
On Friday, Hammond told Sky News television that Britain needed a "middle way" to protect businesses and jobs - outside the customs union, but refusing to "sever our trade links" with the EU.
"There is a growing view that for domestic reasons [the British] want to play everything long and avoid making hard choices that will antagonise the Eurosceptics or give Jeremy Corbyn an advantage", one senior European diplomat told the Guardian.