The cross-party group of politicians hope to introduce a draft law when Parliament returns from its summer recess this week to force Johnson to delay Brexit again if he can’t broker a new deal with the EU by the Oct. 31 deadline.

“We’ve kept the bill as short and simple as possible in order to appeal to as many MPs as possible,” Rebecca Long-Bailey, the opposition Labour Party’s spokeswoman on business told BBC radio on Monday. She called Johnson’s decision to shut down Parliament for a month a “constitutional outrage.”

Johnson’s opponents will try to take control of the House of Commons agenda so they can give themselves time to debate and pass their law. It’s a tactic they used successfully earlier in the year.

The legislation would require Johnson to seek an extension to the Brexit deadline if he can’t get a new deal with the EU “by a certain date in October,” Nick Boles, a former Tory minister who now sits as an independent, told BBC radio on Monday.