Nigel Lawson, a former chancellor, is the most senior Conservative to call for Hammond to go, saying: "What he [Hammond] is doing is very close to sabotage".
But Mr Hammond later told MPs that the Treasury was "prepared to spend when we need to spend" on contingency plans for "no deal" outcomes including a possible "bad-tempered breakdown" in negotiations.
But Nadine Dorries was keen to stress that she had been there first, having called for Hammond's head a few days ago.
The call by Margaret Thatcher's long-serving chancellor comes amid growing concerns that Mr Hammond is trying to keep Britain in the European Union by the back door.
"You have to spend money from time to time, and there is nothing more important than preparing for what has always been the most likely outcome", Lord Lawson added.
He said he feared Hammond was undermining the government and advised a reshuffle to remove him. I fear that he is unhelpful.
"He may not intend it, but in practice what he is doing is very close to sabotage", Lord Lawson, a leading Leave campaigner said.
The former Chancellor called on Theresa May to act, branding his successor "grossly irresponsible" for refusing to spend many millions now to prepare for an exit with no deal struck with the EU.
Many in Westminster reckoned that Lawson was taking his cue from the Daily Mail, which published a scathing editorial this morning calling Hammond "dismal, defeatist [and] relentlessly negative" and even went as far as suggesting that he could be replaced by Jacob Rees Mogg.
She said she wanted a Chancellor who gave an "upbeat message" about the economy and Brexit.
Asked about Lord Lawson's comments, the prime minister's official spokesman said: "The prime minister respects the views of all her Cabinet colleagues".
The Chancellor said there was a "need for speed" from the other 27 European Union nations in agreeing a transition to the post-Brexit era, both to deliver certainty for businesses and to avoid wasteful government spending on contingency planning.
Liam Fox, the trade secretary, insisted there was no difference between him and Hammond, but stressed that there was a need to invest in facilities and staff that might be required if the United Kingdom leaves the European Union without a deal - such as lorry parks and customs operations.
"We don't have that", she said.