In a Conservative Party conference speech full of idealistic language but interrupted by a prankster, May said the election campaign had been "too scripted, too presidential."
"I led the campaign, and I am sorry," she said.
The Conservatives are in a sour mood after June's snap election, called three years early in hopes of bolstering the party's majority in Parliament, saw May's government reduced to a minority administration. The poor result has left May weakened and struggling to unite a government divided over Brexit and other issues.
In a bid to appeal to middle- and lower-income voters, May promised to put a price cap on energy bills and to get government back into the business of building public housing. British governments, including Conservative ones, built hundreds of thousands of homes in the decades after World War II.
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But Conservative Prime Minister Margaret Thatcher's decision in the 1980s to allow properties owned by local authorities to be sold to residents marked a major shift, and in the last two decades successive governments have largely left house-building to the private sector.
Rising prices have made home ownership an increasingly elusive goal for many, especially in London and other big cities.
May needed a strong speech to help fight off rivals to her job, including ambitious Foreign Secretary Boris Johnson.
But the address did not go entirely to plan. May struggled with a cough and a hoarse voice that forced her to pause repeatedly.
Midway through the speech a prankster walked up and handed May a P45, the form given to people being laid off.
As he was bundled away by security, the joker, identified in media reports as comedian Simon Brodkin, said "Boris told me to do it."