Mr Gould, Mr Blair's pollster and strategist, told The Independent that he wanted Labour to build a "progressive coalition" that would be in power for most of the 21st century.
Although this could be done without a Lib Dem alliance, Mr Gould would rather have them on board. "The way I favour is for the Labour and Liberal parties and traditions to move closer together, undoing the fissure that happened in the early part of this century," he said.
"The fundamental reason why Labour has been out of power is that the two progressive traditions split. If they can be brought together, it will undo a century of division and make possible a century of progressive dominance."
Mr Gould's book, The Unfinished Revolution, is to bepublished next week. Although it gives an insider's account of Labour's long path back to power, it also provides a route map for the future of Blairism and will be seen as an indication of the Prime Minister's long-term thinking.
In the book, Mr Gould calls for Labour and the Lib Dems to "converge, effectively becoming one party". Asked yesterday whether this meant the two parties becoming one, he replied: "It may do, it may not. My opinion is that the two progressive traditions can be joined. Ideally, they would be."
Mr Gould said the new coalition would be "so broad that it marginalises the Conservatives, shunting them to the irrelevant extremes of British politics".
He envisaged that Mr Blair might hook in some Tories, particularly over Europe. "Building a progressive coalition does potentially include the likes of Kenneth Clarke and Michael Heseltine."
Labour left-wingers will not welcome his call for closer links with other parties; nor hisview that the grand coalition should be based on "a new middle class politics".
Gould is adamant: "New Labour is not about spin or superficiality, but building a new politics which has at its core an electoral coalition rooted in the middle class.
"I believe the middle class are not an affluent group living in leafy suburbs, but hard-working families making ends meet under tremendous pressure, trying to bring up kids while two parents work, trying to improve their lives. These are the people Labour now represents."
He insisted that it did not mean abandoning Labour's traditional supporters. "The politics of the middle class does not exclude the working class; the middle class have to be at the centre of the coalition because you cannot form a government unless you have the support of the middle class."
But where does that leave people living in "breadline Britain"? Mr Gould claimed: "Our values are those of social inclusion. That is central to Blair's project and the politics of the middle class because they know that our society has been fragmenting."
In his book, Mr Gould adopts Trotsky's maxim of "permanent revolution", saying Labour must never stop modernising.
The Unfinished Revolution by Philip Gould, published by Little, Brown on 29 October.Reuse content