Senior MPs opposing a no-deal Brexit sought assurances from the EU that their bid for a three-month delay would be granted, it has emerged.

European leaders were sounded out before MPs, including the “rebel alliance”, passed a bill, which is expected to receive royal assent on Monday, forcing Boris Johnson to ask for an extension. However, those involved said there were no guarantees in a process that was changing by the day.

It comes as the rebels, including former Tories who have been thrown out of the party, prepare for a legal battle in case the prime minister attempts to defy a law forcing him to ask for an extension on 19 October. The UK is due to leave the EU on 31 October, but the new law would envisage a Brexit extension until the end of January 2020.

Opposition parties have agreed to block a general election before a Brexit extension has been agreed.

The sounding of EU leaders over an extension has angered Tory Brexiters. The Conservative MP and former cabinet minister David Jones said: “Senior EU figures gave private assurances to British MPs, as a consequence of which they supported the surrender bill. This confirms the level of EU interference in our internal affairs and makes the need for Brexit all the more pressing.”

On Friday, Johnson said he would not seek another extension from Brussels, as the incoming law compels him to do if no agreement is in place by 19 October. “I will not. I don’t want a delay,” Johnson said.

David Lidington, the de facto deputy prime minister when Theresa May was in Downing Street, said it would set a “dangerous precedent” if Johnson chose to break the law. Lidington, a former Europe minister, told BBC Radio 4’s Today programme he did not think Johnson would be willing to break the law. “I cannot believe it will come to that,” he said.

The Aylesbury MP, who voted for a general election this week, said the prime minister time should be given the time to secure a deal with the EU.

He said: “I understand why the PM is opposed to this [Brexit delay]. Having talked to him – it is no secret I have differences with him on European policy – I was persuaded that he was serious about getting a deal.

“He basically said to me, please give me until the European council to really get in there and negotiate that deal and come back to parliament. My decision was I would give him that opportunity to get that deal.

“It is such a fundamental principle that we are governed by the rule of law that I hope no party would question it. Defying any particular law sets a really dangerous precedent.”