General election coverage made many viewers switch off
The minister said the corporation had a duty to be "imaginative" in attracting viewers back to politics - but should not sacrifice Westminster coverage in the search for ratings.
The distinction between the BBC and commercial channels "should become sharper", she told the Daily Telegraph.
The BBC has made controversial changes to its news and current affairs output in recent years, including moving Panorama to Sunday nights, and moving the Nine O'Clock News back to 2200.
Ratings war
But the corporation says the move has halted a long-term decline in the news audience - and that the Ten O'Clock News has kept the five million audience enjoyed by the Nine O'Clock News.
There is also an increasingly bitter battle of words about the TV ratings war between the BBC and ITV - and criticisms that the BBC could prejudice its public service mission in the search for bigger audiences.
"The BBC is more commercially focused than it's ever been," ITV's director of channels David Liddiment said recently.
Ms Jowell told the Daily Telegraph that the BBC would be wrong to use entertainment programmes to fight a ratings war with commercial channels.
"The money that goes to the BBC through the licence fee is venture capital for the nation's creativity and that's how it should be spent."
"Its role is qualitatively different from other broadcasters. That distinction should become sharper," she said.
The BBC recently celebrated the first year in which BBC One won a higher audience share than ITV1.
'Civic life'
Figures from the Broadcasters' Audience Research Board (Barb) for 2001 showed BBC One's share of viewing at 26.8%, compared to 26.7% for ITV1.
But Ms Jowell reminded the BBC of its public service remit and licence fee, and said the corporation has an "important part to play in civic life".
"Just because people say they are turning away from politics, that they're apathetic and negative, is not a reason for the BBC to stop covering politics.
"The job for the BBC is not to disengage from politics but to find new ways of engaging the public in democratic debate," she said.
The BBC maintains its current review of its political coverage, by former Newsnight editor Sian Kevill, is an attempt to attract disillusioned viewers back to politics.
Director General Greg Dyke has said programmes have concentrated too much on inward-looking Westminster matters.
And a report by the Independent Television Commission showed that 70% of the public had little or no interest in the television coverage during the 2001 general election.
This compared with 56% at the 1997 election, the report said.
Turnout in the June poll was the lowest since 1918, with fewer than 60% of the electorate voting.