Sir Ed Davey, the leader of the Liberal Democrats, has ruled out a formal pact with Labour to encourage tactical voting in order to beat the Conservatives in the byelections triggered by Boris Johnson and Nadine Dorries’ shock resignations. Dorries, one of Johnson’s fiercest cheerleaders, quit parliament on Friday after being told she would not be elevated to the House of Lords in Johnson’s resignation honours list. Johnson followed suit hours later, ditching his outer-London seat with a bitter resignation statement accusing Rishi Sunak of leading a government that is “not properly Conservative” and attacking the Partygate investigation. The Lib Dems insist they are ready to fight for Dorries’ rural Mid Bedfordshire seat, which is considered safe, and Johnson’s previous constituency, Uxbridge, putting up candidates in both byelections. Davey said: “We’ll stand candidates in both those elections and we’re going to take on the Conservatives on their dreadful record. There’ll be no pacts, no deals. We will fight both byelections. Voters will make the decision. “They’ll decide which party is best placed to beat the Conservatives. We’ll put our case in both constituencies.” A loss in Dorries’ safe seat, which has a majority of 24,000, would prove severely damaging to Sunak’s premiership. Johnson won a 7,000 majority in the Uxbridge and South Ruislip seat that has been Tory since it was formed in 2010. It is now a key target for Labour. There had been speculation that he was seeking a much safer seat before the general election, with Henley being touted as a potential choice. Some of Johnson’s allies had previously speculated privately that he would be better off relocating to Mid Bedfordshire, Dorries’ seat. But this has been ruled out since he quit parliament. The Lib Dems are understood to be hopeful of winning Mid Bedfordshire, claiming they would need a smaller swing to achieve another historic byelection win. The byelection in Uxbridge will also prove another big electoral test for Keir Starmer’s Labour, with the candidate Danny Beales, 34, admitting the party will need to work “exceptionally hard” to win the seat for the first time. Beales has described himself as a “pragmatic socialist” and says he is keen to shift the focus away from internal Labour politics and towards the community he needs to win over. Reflecting on Johnson’s resignation, Davey added: “Boris Johnson believed himself to be above the law. He treated the British public with contempt, partying while the nation grieved.” Starmer told supporters in Uxbridge in an email on Saturday that Labour “now has an opportunity to deliver a historic victory”. “One that will send a real message about the sort of country we want to see, where decency and respect in our politics matters,” he said. “Rishi Sunak knows this moment is critical and will throw everything at it. We cannot let the Tories outspend us. They cannot have that advantage.”