Tory leadership contender Jeremy Hunt has said if he becomes prime minister he will decide at the end of September whether to continue Brexit talks with Brussels or go for a no-deal withdrawal option.
The Foreign Secretary also said he would cancel August leave for Whitehall officials involved in Brexit preparations if necessary.
Mr Hunt said he would launch an all-out diplomatic effort to cut a new deal with the EU if he beats Boris Johnson in the race for Downing Street.
He said he would make a decision on Brexit talks by September 30, ahead of the withdrawal date of October 31.
The Cabinet minister said: “It is important that the EU knows that we will do what it takes to make a success of a no-deal Brexit.
“We won’t blink as a country. That no-deal Brexit is not going to be an opportunity for them to successfully turn the screws on our country.
“I will start engaging with the EU straight away, throughout August.
“Then, when we have published our plan for a deal we think we can get through Parliament by the end of August, we will start formal negotiations in September.”
He added: “There is a hard deadline in what I have said, by the end of September, I, as Prime Minister, will make a judgment as to whether there is a realistic prospect of a deal that can get through Parliament in the short-term.
“And, if my judgment is that is not the case, talks will stop and we will put our heads down and focus on no-deal.”
Mr Hunt’s remarks on possibly cancelling summer leave for civil servants provoked criticism.
The Foreign Secretary said: “All August leave will be cancelled unless I have a signed letter from the relevant permanent secretary saying that all preparations in his or her department are on time and on track.”
However, Dave Penman, general secretary of the FDA union which represents senior managers and civil servants told the Press Association: “Frankly, it’s ludicrous.
“It is just macho posturing with Boris Johnson. He is just trying to outdo Boris on who can look the toughest.
“Of the 400,000 civil servants, 95% are not even involved with Brexit.”