Mr Miliband and Andy Sawford, his party's candidate to take over Louise Mensch's former seat, listened to the views of residents at a voter's house in Great Oakley yesterday.
They discussed local concerns such as Kettering Hospital and unemployment over a cup of tea with Paul and Barbara Webb.
Mr Miliband and Mr Sawford then went on the canvassing trail in nearby streets, continuing the pledge to knock on every door before next month's poll.
Speaking about his hopes of a by-election win on November 15, Mr Miliband said: "I'm optimistic. We're getting a good message on the doorstep but it's a tough fight and by-elections are always tough, particularly when you're trying to take a seat off another party. We've got a long way to go and a lot of work to do."