Hillary Clinton and Bernie Sanders have agreed in principle to contest four more Democratic presidential primary debates.

Should the Democratic national committee sanction the move, the new schedule would begin with a proposed “unsanctioned” debate on 4 February in New Hampshire, hosted by the New Hampshire Union Leader and MSNBC.

Three more debates would then follow this spring, in a development that was first reported on Saturday by Buzzfeed.

The Clinton campaign’s chairman, John Podesta, said in a statement on Saturday one of the debates should be held in Flint. The Michigan city is still in the grip of a crisis over lead pollution in drinking water that has brought great pressure to bear on the state’s Republican governor, Rick Snyder.

Podesta said: “We should use the spotlight of the presidential campaign to keep the focus on Flint, and to lift up the historic underlying issues that Flint and too many other predominantly low-income communities of color across America are struggling with every day.

“We want their voices to be heard in this campaign, and holding a debate in Flint would go a long way toward achieving that goal.”

The Sanders campaign proposed adding the four events – one each in February, March, April and May – after criticizing the DNC for scheduling thus far low-rated debates on weekends and holidays.

The third remaining Democratic candidate, Martin O’Malley, has also strongly criticised the DNC for what he says is an attempt to limit the number of debates, thereby tilting the Democratic primary in favour of Clinton.

The addition of four more debates would bring the total of Democratic contests up to 10. The Republicans are due to hold 12 debates.

On Saturday, both campaigns said a final deal had not yet been reached and the DNC had not signed off on the agreement.

A New Hampshire debate on Thursday would give Clinton and Sanders a high-profile encounter before the nation’s first presidential primary.

The next scheduled debate will be held Milwaukee, Wisconsin, on 11 February, two days after the New Hampshire primary and less than two weeks before the South Carolina Democratic primary. A debate is also scheduled for Miami on 9 March.

Clinton and Sanders are in a tight race before Monday’s Iowa caucuses. Clinton trails the Vermont senator in New Hampshire but leads healthily nationally.