Boris Johnson has said the possible abolition of the BBC licence fee needs "looking at"
Speaking at a rally in Sunderland, the prime minister questioned how much longer funding a broadcaster out of "a general tax" could be "justified".
Ministers have agreed the licence fee will stay in place until at least 2027, when the BBC's Royal Charter ends.
Mr Johnson was asked by a member of the public whether he would consider axing all TV licences.
The prime minister said that, while he would not make up policy with three days to go before the election, it was an issue that was worth "looking at" in the future.
"You have to ask yourself whether that approach to funding a media company still makes sense in the long term given the way that other organisations manage to fund themselves," he said.
"The system of funding out of what is a general tax bears reflection. How long can you justify a system whereby everybody who has a TV has to pay to fund a particular set of TV and radio channels."