UK opposition parties have agreed not to back Boris Johnson’s demand for a general election before the EU summit in mid-October.

Labour, the Lib Dems, the SNP and Plaid Cymru say they will vote against the government or abstain in Monday’s vote on whether to hold a snap poll.

But the PM said the parties were making an “extraordinary political mistake”.

Meanwhile, a bill designed to prevent a no-deal Brexit has been approved by the House of Lords and will pass into law.

It will force the prime minister to ask the EU for the Brexit deadline to be extended beyond 31 October if no deal is agreed by the UK and Brussels by 19 October.

Mr Johnson wants an election to take place on 15 October, ahead of that date and the EU summit on 17 and 18 October.

He argues that a snap poll will allow the government to “get on” with delivering Brexit by the end of October.

But opposition MPs – who, along with Conservative rebels, have already defeated one attempt by the government to bring in an early election – say Mr Johnson is trying to push through a no-deal exit.

During the past week the prime minister has suffered several defeats over Brexit in Parliament, expelled 21 of his own MPs for rebelling and seen his younger brother, Jo Johnson, resign from government.

In other developments:

• Mr Johnson’s decision to prorogue – suspend – Parliament next week ahead of a Queen’s Speech on 14 October is being challenged in the courts in Scotland and Northern Ireland. Scotland’s Court of Session will give its judgement next week.
• Campaigner Gina Miller has lost a judicial review she brought to London’s High Court over the prorogation. However, permission has been granted for the case to be heard in the UK Supreme Court on 17 September.
• The chief constable of West Yorkshire said he was “disappointed” his officers were used as a backdrop to a speech by Boris Johnson about Brexit in Wakefield.

Following the meeting of opposition parties on Friday, a Labour Party spokesman said: “Jeremy Corbyn hosted a positive conference call with other opposition party leaders this morning.

“They discussed advancing efforts to prevent a damaging no-deal Brexit and hold a general election once that is secured.”