Opposition party leaders are due to meet in Westminster later to discuss how to stop a no-deal Brexit.
They are expected to discuss a plan by Liberal Democrat leader Jo Swinson to force the PM to seek a Brexit extension as early as this weekend.
But the SNP want a no confidence vote straight away and Plaid Cymru is considering pursuing impeachment.
The chancellor has said a no-deal Brexit “may well happen” on 31 October, despite a law aimed at avoiding it.
The law, known as the Benn act, forces the government to ask for an extension to the Brexit deadline if a deal is not agreed by 19 October, the day after a two-day EU summit.
Chancellor Sajid Javid told BBC Radio 4’s Today programme that “every government should observe all laws at all times”, adding: “We’re taking a careful look at that law.”
“We’re also very clear that our policy has not changed. We will leave on October 31,” he said.
“And if you are going to ask me next, how we going to do that? We’re not going to set that out right now.”
Mr Javid said there could be no more “dither and delay and we will leave if we have to without a deal on October 31”.
When asked if he knew how the government would be able to bypass the Benn act, he said: “I think I do.
“The intention of the law is clear and I do think it has absolutely made it harder for the government to get the deal that we all want to see. That said, it can still be done.”
But independent MP Nicholas Soames, who was expelled from the Conservative Party after rebelling against the PM in a bid to prevent a no-deal Brexit, said the Benn act was “watertight”.
“Quite how they propose this (a no-deal Brexit) to happen is a mystery,” he told BBC’s Victoria Derbyshire programme.
“The prime minister and the government must obey the law and Parliament will make sure that happens.”
He said if there was a “reasonable deal” brought to Parliament he would support it.
Another rebel, former Tory MP Dominic Grieve told Sky News that Mr Johnson would be “dismissed” as prime minister by the Queen if he fails to seek a delay to Brexit in the event he has not secured a deal by 19 October.
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Labour’s shadow health secretary Jon Ashworth told BBC Radio 4’s Today programme opposition parties were “prepared and ready in Parliament to respond to anything that comes out of Downing Street”.
On Sunday, SNP MP Stewart Hosie told the BBC that a vote of no confidence in the government aimed at replacing Mr Johnson as prime minister could be held this week.
He said such a move may be the only way of avoiding a no-deal Brexit on 31 October.
And SNP leader Nicola Sturgeon hinted on Friday she might back Jeremy Corbyn becoming a “caretaker” prime minister.
But this does not have the backing of the Lib Dems, who said the Labour leader is too divisive to have the role.
Meanwhile, Plaid Cymru leader Adam Price has said MPs “cannot allow the principle to be set that the prime minister can deliberately mislead us and get away with it”.
Speaking on the Victoria Derbyshire programme, Mr Price set out reasons why he believed the prime minister should be impeached: “Those who lead us cannot mislead us without accountability.
“It comes to the question of whether he told the truth. Scottish law lords came to the conclusion that the reasons he gave [to prorogue parliament] were not true, they were deliberately false.
“We need accountability for those untruths.”
Mr Price said impeachment was being discussed with other opposition MPs, but he couldn’t say how many backed the move.
Impeachment can lead to ministers being put on trial in Parliament for high crimes and misdemeanours beyond the reach of law or normal prosecution, if MPs vote for it.
In 2004, Mr Johnson backed calls for Tony Blair to be impeached over the Iraq war, but the procedure is considered “obsolete”, according to House of Commons library, as it has been superseded by other forms of ministerial accountability, so it would be unlikely to succeed.
What is the Benn Act?
When Mr Johnson talks about the “surrender bill”, he is referring to the European Union (Withdrawal) (No. 2) Act, also known as the Benn Act after Labour MP Hilary Benn, who introduced the legislation to the Commons.
The act – which became law earlier this month – stipulates the prime minister will have until 19 October to either pass a deal in Parliament or get MPs to approve a no-deal Brexit.
Once this deadline has passed, he will have to request an extension to the UK’s departure date to 31 January 2020 from the EU.
If the EU responds by proposing a different date, the PM will have two days to accept that proposal. But during this two-day period, MPs – not the government – will have the opportunity to reject the EU’s date.