Mr Portillo's seat would be vulnerable to tactical switching by the Liberal Democrats to Labour, but Peter Mandelson, Labour's campaign chief, yesterday rejected talk of tactical voting.
The Liberal Democrat leadership last night also refused openly to encourage tactical voting, although they made clear that they expected it to happen at grass roots level.
Tony Blair will kick off the final week of campaigning today with warnings about the threat of a fifth Tory term with a press conference claiming that the Tories would break up the NHS. That is likely to lead to renewed howls of protest from the Tories, who are still fuming over Labour claims last week that they would abolish the state pension.
Labour strategists will shrug off complaints that the campaign has been too negative, and turns off voters. They are relying on private polling evidence showing they are heading for an overall majority, irrespective of whether "don't-knows" go back to the Tories.
Mr Mandelson said Labour believes there are between 10 and 15 per cent of "don't- knows" still to be won over - half the amount the Tories estimate could decide the outcome of the election.
Labour's campaign team is also buoyant with confidence on private polling showing that the issues of education and health, and Tony Blair's personal leadership, are killing the Tories' support.
The Tories dispute Labour's claims, insisting that John Major's personal crusade is showing his strength of leadership. But Labour claimed that Mr Blair's personal lead over Mr Major has increased by 22 per cent since the election began.
Tory divisions over Europe are also contributing to the switch to Labour, according to Labour's polling, which shows that 80 per cent think the divisions are more important than the substance of what they are saying on Europe - a finding at odds with some of the anecdotal evidence in The Independent's own survey last week.
Labour claims it has a 12 per cent lead on "standing up for Britain's interests abroad", with a 19 per cent lead on improving living standards at home. Its polling shows that Labour is winning over younger women.
The Liberal Democrat leadership will today make an explicit appeal to "One Nation" Tories by fielding two Tory defectors, Peter Thurnham and Emma Nicholson, at a press conference to launch the final week of their campaign.
Liberal Democrat strategists claimed Paddy Ashdown's campaign on promises to increase taxes to improve health and education is drawing traditional Labour support in its key seats. "The talk of a Labour landslide is making people feel Labour will be in for a long time and they need Liberal Democrats in Parliament to make a real difference," said one senior Liberal Democrat source.
Labour moved last night to head off an attempt by the Tories to repeat their 1992 "tax bombshell" attack on Labour in the final days of campaigning. Alistair Darling, a Labour treasury spokesman, issued a leaked Tory analysis of their own manifesto, showing that commitments, including the target of reducing the standard rate of income tax to 20p in the pound would cost pounds 9.8m, but the money had not been found.Reuse content