Labour is planning to target the south of England heavily at the general election as the local election results show some “blue wall” seats are turning red, Keir Starmer’s election chief has said. The shadow cabinet minister Pat McFadden said Labour was advancing in southern Tory heartlands and it was wrong to think the Lib Dems were the only challengers to the Conservatives in the south. Speaking to the Guardian, he said it was now the case that Labour “controls twice as many councils in the south-east as the Tories”, pointing to gains in Rushmoor, Crawley, Swindon, Thurrock, Basildon and Southend. “The story of parts of the blue wall turning red is under-noticed,” he said. Thursday’s local and mayoral elections had given Labour the “confidence and belief” that it can win a general election convincingly, he said. Rishi Sunak faces turmoil in his party after its heavy losses, as the rightwing former home secretary Suella Braverman said the prime minister’s “plan is not working” and “at this rate we will be lucky to have any Conservative MPs at the next election”. Sunak faces a schism over whether to swing to the centre to tackle the threat from Labour and the Lib Dems or the right to try to squeeze Reform UK’s vote share. Labour’s targeting of the south shows its spreading ambition after winning convincingly in the local elections across much of the “red wall” in the north and Midlands won by Boris Johnson in 2019. It had a landslide 26% swing at the Blackpool South byelection and took the mayoralties in the North East, East Midlands, West Midlands and York and North Yorkshire. The Lib Dems made gains across the south and south-west, adding more than 100 seats and suggesting the party will do well in the home counties at a general election. Labour made advances in areas of Kent and Essex, as well as councils such as Rushmoor, which includes the garrison town of Aldershot. Downing Street insisted on Sunday that the prime minister would not be changing direction and wanted to stick to his plan. Braverman called for a campaign to leave the European convention on human rights and set a migrant cap, but acknowledging it was too late to oust Sunak while admitting she regretted having backed him for the leadership. Her ally, the Tory MP John Hayes, suggested a reshuffle was needed to bring back major figures from the right. The transport secretary, Mark Harper, one of Sunak’s supporters, pointed to analysis by the polling expert Michael Thrasher saying the local results showed Labour only had a nine-point lead. “There is a fight to be had,” he told broadcasters. “The next election is not a foregone conclusion.” Sunak seized on the same analysis, urging the Tories to “come together as a party and show the British people we are delivering for them”. The prime minister told the Times that a coalition of Labour, the SNP, the Lib Dems and the Greens “would be a disaster for Britain”. Other experts, however, said it was not possible to translate the local election vote in England to national results across the whole of the UK because people vote for different parties at a general election. As there were no elections in Scotland, the analysis also assumes Labour would win a solitary seat north of the border as it did in 2019. Recent polling suggests the party could in fact take more than 20 seats. The Conservatives lost almost 474 council seats compared with the last local election count, while Labour gained 186, the Lib Dems 104, the Greens 74 and independents 145. Reform won just two council seats but got a high vote share in some areas where the party stood. It came within 150 votes of the Tories in Blackpool South. McFadden said Labour had pursued a strategy that was “ruthlessly focused on the seats and the councils that will make a difference and there was no better example than in the West Midlands where we put a lot of resources in knowing it was on a knife edge. That organisational effort helped us get over the line. “I’m always the first person to say of course there’s more work to do, but apart from the results which were tremendous and beyond our expectations one of the results of the last few days is to give us a confidence and belief that we haven’t had for a long time. “Because Labour has got too used to losing, and even some of its own supporters and voters have said we support Labour but we always lose. But what the weekend’s results show is that Labour doesn’t have to always lose and the Tories are beatable … we go into it with more belief because of what’s happened in the past few days.” The results were not uniformly positive for Labour. Parts of the country turned to independents and the Greens, particularly where some voters were disappointed with Labour’s stance on Gaza. Labour lost its majority on Oldham council, and its vote share in the West Midlands was dented by support for the independent candidate Akhmed Yakoob. McFadden said: “I understand why people feel strongly about this issue because it’s a humanitarian crisis and we want to help those people in Gaza who are affected by that. But two things have affected our position all the way along: one is defending Israel’s right to defend itself in the face of what happened on October 7 and the second is working for a better future for the Palestinian people. Those two things will continue to inform our position.” With the Tories already claiming Labour could turn to other parties to form a pact in a hung parliament, McFadden said he was clear that would not happen. Asked on Sky News if he could imagine Labour and the SNP working together if his party did not win a majority at the general election, he said: “Our aim is to win a majority, to govern, to meet the mood for change, and we’re not planning any alliances or pacts with anyone.”