With one day to go before the polls open, the prime minister has given his strongest indication yet that National Insurance would not go up in a Labour third term.

Tony Blair made the 11th hour election move to counter lingering fears that his government would raise taxes in the next parliament and could not be trusted.

Having said voters should "not assume" contributions would increase before the 2001 poll and then increasing them by one pence in the pound to pay for increased health spending, Blair said there was no new need for more cash.

"I'm not writing the Budget. But you don't build the same hospital twice," he told Channel 4 news.

"The National Insurance rise takes care of the catch-up that was needed for the health service.

"But by 2008, for the first time the country will be back up to the European average."

Meanwhile, all three party leaders yesterday continued their whistlestop tours of the key marginal seats.

Labour officials say that the Tory threat is now strongest in London, Essex and Kent.

In an article in today's Guardian, Gordon Brown continues to warn Labour supporters against voting Lib Dem.

The chancellor says: "There are real consequences to a protest vote that risks inadvertently returning the Conservatives to power, and which, by punishing Labour, would end up punishing the people who most need Labour."

Labour has also enlisted the support of Tony Benn.

The veteran activist and strong critic of New Labour has been telephoning wavering Labour supporters and urging them to stick with the party.

The Liberal Democrats, meanwhile, have diverted activists from vulnerable and key target seats to other winnable constituencies, thanks to their growing belief that they can increase their number of MPs and share of the vote tomorrow.