William Hague has hit back at Labour leader Ed Miliband's attempt to snatch the mantle of the "one nation" party from the Conservatives.
Mr Miliband grabbed headlines last week by saying he had sought inspiration from Tory Prime Minister Benjamin Disraeli for his new slogan.
Disraeli was associated with a moderate "one nation" brand of Conservatism.
But Mr Miliband's claim was mocked by the foreign secretary as the Tories gathered for their annual conference.
Speaking from the Birmingham conference stage, Mr Hague, a best-selling author of political histories, was cheered by activists as he attacked the Labour leader: "Last week he made claim to be Disraeli.
"We know a little more about Benjamin Disraeli, a great Conservative Prime Minister, than he does.
"Disraeli was defined by changing his party for the late 19th century while Ed Miliband will be defined by refusing to change his party for the 21st century.
"Disraeli believed in fiscal discipline, in self-reliance, in building on historic strengths, in this country paying its way and in taxes being kept down. He was no deficit spender, but was careful to budget for a surplus.
"To borrow a turn of phrase, we were led by Disraeli, our predecessors knew Disraeli, Disraeli's beliefs were Conservative through and through, and, Ed Miliband, you are no Disraeli."
In 1872, Disraeli spoke out in favour of helping "the condition of working men", of government intervention to do so and of taking action - controversial at the time - to heal the divide between rich and poor.
His brand of Toryism became known as "One Nation".
Prime Minister David Cameron is expected to use his keynote conference speech on Wednesday to mount a sustained attack on Mr Miliband's Labour Party, although it is not known if he will directly address the opposition leader's attempt to cast himself as the new Disraeli.
Conservative Party Chairman Grant Shapps has, meanwhile, attempted to fire up activists by telling them "the election starts here".
A countdown clock, which also hangs on the wall of Conservative campaign headquarters, appeared behind him, spelling out that it is 942 days until the next election, expected in 2015.
Mr Shapps said the Conservatives had to get better at talking up what they have achieved.
"Why are we the shy Tories?" he asked.
"We have got to get out there and tell them," he said. "Let's get out there and fight our corner."
Mr Shapps pointed to his own experience in the 2005 election in Welwyn Hatfield, where he turned a 5,000 Labour majority into a 17,000 Conservative one, to emphasise that there should be very few places that Tories regard as no-go areas.