Winning mayoral elections across the country can work as a blueprint for success in a general election, Sadiq Khan will tell Labour conference today.

In his first conference speech since becoming Mayor of London, Khan will make an impassioned case that Labour “will never, ever be good enough” if it is not in power.

Khan won the London mayoralty in a sensational landslide this May, earning more personal votes than any politician in British history as 1.3 million people turned out to vote him in. He is expected to tell delegates that Labour winning devolved elections can show voters how the party can “demonstrate that we can make a real difference to people’s lives” and “prove that we are ready for government”.

He will namecheck recently re-elected Welsh First Minister Carwyn Jones and Bristol Mayor Marvin Rees as a reminder to activists that Labour holds “power in towns and cities the length and breadth of Britain”.

This intervention comes a day after an exclusive poll for LabourList showed the party is currently on course for its worst election defeat since 1935. However, that has done little to dissuade members about the direction of the party, with Jeremy Corbyn comfortably re-elected as leader this weekend.

The new mayoral elections in Greater Manchester, Liverpool City Region and the West Midlands next year should provide Labour with a platform to return to government at the next election, Khan will say. “We have to start by winning the Mayoral elections next year, here in Liverpool, along the M62 in Manchester and down the M6 in Birmingham. Let’s ensure Labour is in power in every great city in Britain.”

He will finish by saying: “Conference, it’s time to put Labour back in power. It’s time for a Labour Government. A Labour Prime Minister in Downing Street. A Labour Cabinet. Labour values put into action.”