Senior MPs who oppose Theresa May’s Brexit deal have met to discuss how to stop No 10 “stitching up” crucial votes that will decide how the UK leaves the European Union.

The cross-party group includes Sir Oliver Letwin, Nick Boles, Yvette Cooper and Hilary Benn, who have already successfully forced legislation to prevent a no-deal Brexit through the House of Commons.

They are now concerned that No 10 could present a series of Brexit alternatives for parliament to vote on – such as May’s deal, Labour’s proposals, or a customs union – without consulting MPs properly about what options should be on the table.

There is growing suspicion that the government is still set on trying to get the prime minister’s deal through parliament if talks with the Labour leader, Jeremy Corbyn, fail.

The Guardian view on the parties’ Brexit talks: to agree is to split | Editorial Read more

May has said she will first try to make a deal with Corbyn, but if that is not successful she will try to agree a process with him to allow parliament to find a solution, as long as Labour also promises to be bound by the result.

Those votes could come early next week, though May will head to Brussels on Wednesday for an emergency summit to ask for an extension to article 50.

Any hope of laying a timetabling motion to hold the votes on Monday appeared to be scuppered on Thursday afternoon after the House of Commons unexpectedly had to adjourn early for the weekend because of flooding in the chamber.

The two frontbenches would be the ones to decide on the options for MPs to vote on, if the votes do take place next week.

A source close to the meeting said: “MPs have to ensure that parliament’s will is not ignored by the government. The suspicion is that the government could use every trick in the book to amend, delay and vote down what has so far gone through the house.”

They are also worried about ensuring the bill preventing a no-deal exit gets passed in the House of Lords. This backbench bill, tabled by Cooper, the Labour chair of the home affairs committee, passed by a single vote in the House of Commons on Wednesday evening and was heard in the House of Lords on Thursday.

Peers furiously debated the snap bill to extend article 50 in a marathon session in the Lords, during which there were several attempts by Eurosceptic peers to filibuster and use other procedures to block the bill’s progression.

On Thursday, the Brexit secretary, Steve Barclay, warned MPs that the Cooper bill could backfire if the Commons rejected any Brexit delay offered by EU leaders at a summit next Wednesday. No 10 sources said there would be no time to renegotiate it before the deadline for departure on Friday.

Labour’s deputy leader in the Lords accused the government of foul play as the bill made its way through the upper chamber, saying there was tacit government support of Tory Brexiters organising filibusters.

Before the bill itself could even be debated, opposition peers defeated several Tory backbench bids to block its progress, but lengthy speeches and procedural devices significantly slowed down proceedings.

Facebook Twitter Pinterest The Labour peer Dianne Hayter criticised Tory attempts to filibuster the bill. Photograph: House of Lords/PA

Late on Thursday evening, peers agreed they could not pass the bill in a single day and proceeded only to the bill’s second reading, with remaining stages taking place on Monday.

Dianne Hayter, the Labour peer steering the bill through the Lords, said peers should not be trying to scupper the will of the Commons.

“There is unfortunately a filibuster being organised by Conservatives to try to ‘talk out’ this bill; they are getting a bit of support, in fact quite a lot of support, from the government, which I think is fairly shameful,” she told Sky News.

Speaking later in the Lords, Hayter said the government had lost the support of the House of Commons and was refusing to follow the instructions of the Lords to proceed with the bill, to chants of “sit down” from the Tory benches.

“The bill can only have effect if we deal with it today so that it can receive royal assent in time for the EU council to consider the application for an extension,” she said.

Michael Forsyth, one of the Conservative peers leading the opposition, said suspending standing orders to fast-track a bill in this way could lead to “tyranny”.

Lord Forsyth also criticised how it was passed in the Commons by just one vote, including that of the former Labour MP Fiona Onasanya, who was wearing an electronic tag. “This is a major constitutional matter. It was passed by one vote,” the former cabinet minister said.

After other peers admonished Forsyth, he continued: “All that lies between us and tyranny is that we respect the conventions of both houses. Why do we do that? Because it is our constitution.”

The Conservative peer and former cabinet minister Nigel Lawson also criticised the procedure. “I have served in parliament for 45 years and there has never been an instance of constitutional vandalism on the scale that we are witnessing today, and at the present time more generally,” he said.

Labour sources are confident the bill has the support to pass through the Lords despite fierce opposition from pro-Brexit Tory peers.

Downing Street has argued that asking parliament to approve any extension to article 50 could increase the risk of a no-deal Brexit by accident. A No 10 spokesman did not explicitly endorse the filibuster in the Lords by Conservative peers but asked them to scrutinise it thoroughly.