The former Party Leader has warned that the Labour Chancellor is too rooted in the past, too wedded to state domination and control, and too vague on the reform agenda necessary to improve our hospitals and schools, to take over from Tony Blair.
The Shadow Foreign Secretary, who is currently in charge of the Party while David Cameron is away on paternity leave, went on: 'The potency of the challenges we face in the next century, including economic competition from rising nations, radical Islam using states abroad, radicals here and networks globally to subvert democracy, climate change posing difficult questions about energy use and economic development, and social change requiring us to rethink obligations across generations and between partners, all require us to have a Prime Minister certain of his own identity, free of ideological baggage from the past, uncompromised by failure in government, sufficiently at ease with Britain that he doesn't need to constantly redefine what Britishness means, sufficiently ambitious for Britain that he doesn't shirk from embracing radical reform, and is clear-sighted about how our common institutions need to be renewed.'
Mr Hague also accused Mr Brown of wrecking the very institutions which have held the nation together for centuries, as he has played a key role in Labour's drive to widen and strengthen state power, reduce individual freedom, suppress innovation, and seek to control, direct, and interfere in all walks of life.
Scoffing at the way the Chancellor has tried to promote 'Project Gordon' by wearing Ralf Lauren-style shirts and Tim Cruise-style flying helmets, Mr Hague questioned whether Mr Brown's traditionally left wing beliefs equipped him to tackle the big challenges facing the country today. He said: 'One of the key problems with the Left is that they develop an analysis of whatever a good society needs to be, and then seek to implement that change through crude mechanisms, which involve a growth in state power, a diminution of individual freedom, a squeezing out of innovation, diversity and creativity, and end in the dogmatic pursuit of targets which events have long rendered redundant.
'By its very nature this approach is stuck in the past - it is inappropriate for the fast-moving world in which we live. And it holds us back from making the changes we need to make to respond to the real challenges of the 21st century.
'If this Left-wing approach of controlling, directing and interfering were simply an alternative set of ideas advanced by socialist nostalgics, it would be our duty as politicians concerned about the country's future prosperity and security to challenge them. But the task of taking on this philosophy has become imperative - because it drives the man everyone expects to be the next Prime Minister.'
'The qualities of left-wing thinking - the tendency to channel, control, organise, direct and boss in conformity with dogma and in a way which inhibits growth and change - are central to Gordon Brown's way of operating.'
Instead of concentrating on getting the economic fundamentals right, and allowing a free market economy to develop and expand, Mr Brown had used the entire tax and benefits system to remake British society and alter British behaviour in conformity with his grand plan for us all, Mr Hague said.
He added: 'This whole approach - the belief that the economy is there for politicians to tell us how to live, rather than generating the wealth which gives us greater freedom to decide how we want to live - is stuck in the past. As I'm afraid, is the Chancellor's approach to public service reform.'
Mr Hague challenged the Chancellor to spell out in detail how he would reform public services, rather than rely on abstract fudges, hedges and muttered generalities. Instead of equivocation, prevarication and endless repetition, the Chancellor should explain how we equip the next generation for the rigours of competition in the 21st century.
'Until we have decisive evidence to the contrary, we'll have to conclude that the only progressive change the Chancellor is really interested in is changing his address,' Mr Hague joked.