Tory rebels against Theresa May’s Brexit plans could ultimately collapse the government, Dominic Grieve has said, ahead of another key week in parliament over the EU withdrawal bill.

Grieve, the former attorney general, has said he objects to a government amendment to the bill which would limit the power of MPs in shaping policy if parliament rejects a final Brexit bill.

Asked if voting against the government could eventually bring it down, Grieve said: “We could collapse the government.” He told BBC One’s Sunday Politics: “And I can assure you I wake up at 2am in a cold sweat thinking about the problems that we have put on our shoulders. The difficulty is that the Brexit process is inherently risky.”

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Grieve, who has drafted his own amendment that would give MPs more scope in directing ministers in the possible event of a likely no-deal Brexit, later clarified to the Press Association that his comments referred to a future vote on a deal, rather than next week’s events.

The ping-pong process of the withdrawal bill between the two houses of parliament returns to the Lords on Monday, when peers are expected to reject the amendment drafted by May and her team, and insert one modelled more closely on Grieve’s idea.

On Wednesday, the amendments will return again to the Commons, where May faces the possibility of defeat over a meaningful vote.

A series of Conservative rebels pulled back from voting against the government last week after the PM promised to listen to their concerns, but then said they felt let down by the eventual government amendment produced on Thursday.

Grieve said: “I can’t save the government from getting into a situation where parliament might disagree with it.

“The alternative is that we have all got to sign up to a slavery clause now saying whatever the government does, when it comes to January, however potentially catastrophic it might be for my constituents, and my country, I’m signing in blood now that I will follow over the edge of the cliff. And that, I can tell you, I am not prepared to do.”

The government’s prospects of defeat were increased last week when the junior justice minister Philip Lee resigned his post so he could vote against the minister on a meaningful vote. He ended up abstaining after the promise of a compromise.

In an interview broadcast on Sunday, Lee said he planned to back Grieve’s amendment, and indicated that other ministers could be prepared to follow his example.

“My intention is to support Dominic Grieve in the amendment that he put before the house, because that’s what I publicly stated last Tuesday,” he told Sky’s Sophie Ridge on Sunday show.

“This amendment I guess may be amended and if that is acceptable I will support that but fundamentally I resigned to support parliament getting a proper truly meaningful vote on the deal to leave the European Union.”

Lee said he had had “conversations with ministers at all levels who are concerned about the direction of travel”. He said he did not know whether any immediate resignations could happen, but added that others did have serious worries.

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The rebels were angered after the government amendment offered parliament the opportunity only to vote on a “neutral motion” stating that it has considered a minister’s statement on the issue, if a deal is rejected.

It would not be possible to amend the motion, meaning that MPs could not insert a requirement for May to go back to the negotiating table or extend the Brexit transition.

In an interview with the prime minister, broadcast on Sunday, May rejected the idea she had double-crossed her rebels.

“I did indeed meet a group of my fellow MPs,” she told BBC One’s Andrew Marr Show. “I listened to their concerns and I undertook to consider their concerns.

“And the next day I stood up in prime minister’s questions and said I’d put an amendment down in the House of Lords. I’ve done exactly that. We recognise the concerns people have about the role of parliament.”

She added: “Parliament cannot tie the hands of government in negotiations.”