Senior British ministers presented a united front to negotiations with the European Union on Sunday.
British ministers are to publish a new series of detailed papers setting out their aims for the Brexit talks amid criticism about a lack of clarity on the government's negotiating position. The UK wants to start talking about its post-Brexit relationship with the EU in order to reassure anxious businesses, citizens and investors, but the union has insisted that first exit arrangements should be determined.
After a summer of ministerial feuding, Mr Hammond, who favours a "softer" pro-business Brexit, came together with International Trade Secretary Liam Fox, from the Brexiteer wing of the party, to declare there could be no "back door" attempt to keep Britain in the EU.
The first set of position papers, to be published from this week, will include one covering the Border between Northern Ireland and the Republic after the United Kingdom has left the EU.
Officials said the papers would show the British government was ready to "broaden out" the negotiations and move forward towards a deal that worked for both sides.
Writing in the Mail on Sunday, Soubry said: "If the prime minister or her successor [in the event of May standing down] is not prepared to confront the ideologues, I gravely fear that the party could split - and that would change Britain's political landscape completely".
"We've been crystal clear that issues around our withdrawal and our future partnership are inextricably linked", a source in Britain's Brexit department said.
The bloc's chief negotiator, Michel Barnier, said last month there was "a clock ticking" on the talks.
Since May lost her parliamentary majority in a election gamble in June, infighting between members of her cabinet has appeared, with disagreements on issues including whether freedom of movement of European Union nationals should continue after Britain leaves the bloc in 2019.
Free movement for Irish citizens in and out of Britain is expected to continue after Brexit, with the establishment of a Schengen-style area between Ireland and Britain created to resolve the border problem. But the British government rejected the report.
"We will leave the single market, because there was a vote for change on 23 June and that is what we will deliver".
The UK formally triggered the Brexit process on March 29 and divorce negotiations officially began on June 19.
Brexit Secretary David Davis was warned by an European Union chief last night that he would be putting the security of British people at risk if he pulled out of pan-European crime-fighting agreements.