The next Conservative leader must immediately extend Britain’s EU membership and draw up a new Brexit deal with Labour MPs, a key powerbroker in the party’s leadership race has demanded. In a significant intervention that will be seen as a warning to candidates embracing a no-deal Brexit, Amber Rudd, the work and pensions secretary, who is regarded as the leading pro-European voice in the cabinet, calls on all contenders to concede that Britain will not leave at the end of October and start work on a new deal with Brussels. Writing for the Observer, she warns candidates they will lose should they “enter into another battle with parliament over no deal on 31 October”. She says the new leader will have a “brief opportunity to reset the political agenda” with the EU, which should be used to craft a deal that enough backbench Labour MPs would back. “We need to start being honest,” she writes. “The starting point is that we are not leaving on 31 October with a deal – parliament will block a no-deal Brexit, and there isn’t time to do a revised deal. “Many good Conservative colleagues will raise their hands in despair at my suggestion that…