Tory strategists have boosted the number of “spies” sent to “dig up dirt” on the Labour party at what could be the final conference season before the next general election, sources have told the Guardian. The Conservatives and Labour usually permit two official “observers” to attend each other’s autumn conference. But this year, Conservative Campaign Headquarters (CCHQ) is said to have dispatched at least half a dozen more helpers to Liverpool to assess Labour’s strategy. They have been tasked with infiltrating fringe events taking place outside the secure zone – meaning they do not need an official pass to gain entry – and record any comments by Labour MPs and activists that could be used to attack the party. One source described the task as being to “dig up dirt” to embarrass Keir Starmer, the Labour leader. Another said they were ready to “mingle with donors” to understand how far some Tory sponsors’ frustration with the Conservatives could push them to give money to Starmer’s party. Philip Harris, known for his Harris academy schools, switched from donating to the Tories by making a £5,000 contribution to the shadow chancellor, Rachel Reeves, and has criticised the Tories over their lack of “clear vision”. John Caudwell, the biggest donor to the Conservative party before the last election, has said he would not back Rishi Sunak after the “madness” of the prime minister’s U-turn on green policies. Caudwell said he was thinking about switching to Labour instead. Labour figures are understood to be poring over Starmer’s record as director of public prosecuions, looking over the cases he was involved in to hit back at any attacks CCHQ will use during the election campaign. Tory jitters have been compounded by their conference in Manchester last week which included Tory infighting over LGBTQ+ rights, migration and tax cuts. They fear that, in contrast, Labour’s conference will be “dull as dishwater” – with MPs stringently on-message, sensing that any slip-ups could cost them their significant poll lead. A Labour source said: “It’s flattering that the Tories are following in the footsteps of business and donors by letting people know they are flocking to Labour conference. It is a reminder that they were the future once.” Party conference is a vital fundraising tool for political parties, allowing them to court businesses leaders, donors and stakeholders. With a general election due to be held by January 2025 at the latest but said to be most likely to come next autumn, this year’s autumn conferences could be the final ones of this parliament.