The Prime Minister is to stress the importance of “unity of purpose” ahead of the start of Brexit negotiations, saying the country faces the most “challenging” period in her lifetime.
“It is the responsibility of leaders to be straight with people about the challenges ahead and the hard work required to overcome them,” she will say.
“As we embark on the momentous journey ahead of us over the next few years, our shared values, interests and ambitions can - and must - bring us together as a united country.”
The Tory manifesto is also expected to put forward an “uncompromising” message on immigration, reports the BBC.
Mrs May will say that high immigration levels can harm community cohesion and restate her commitment to bringing net migration down to the tens of thousands.
It is also expected that manifesto will promise to “bear down on immigration from outside the EU” across all visa routes.
Firms will be asked to pay more to hire migrant workers, who will in turn be asked to pay more to use the NHS.
And according to the BBC, there are unconfirmed reports that the commitment not to raise income tax, VAT or national insurance, made at the 2015 election, will be ditched, with a revised timetable introduced aimed at eliminating the deficit and balancing the books by the middle of the next decade.
The Prime Minister will announce a number of other domestic policies, not all of which will apply directly in Scotland due to devolution.
She will promise to address the rising cost of social care in England, promising no-one will have to sell their property in their lifetime to fund residential or home care.
Instead, the cost of care - above a £100,000 threshold - will be taken from their estate when they die.
Winter fuel payments, which pensioners currently get irrespective of need, will be also means-tested, with the proceeds going directly to care for the elderly.
Universal free school lunches for infant pupils in England will be scrapped, with free breakfasts offered across the primary years.
The SNP said Theresa May wanted a “free hand to dismantle the welfare state and to push through their reckless plans for a hard Brexit which threaten jobs, investment and livelihoods”.
And the Liberal Democrats have nicknamed Theresa May the “lunch snatcher” over her plans to scale back free school meal provision.
Sarah Olney, Liberal Democrat education spokeswoman, said: “Margaret Thatcher was known as the ‘milk snatcher’.
“Theresa May will go down as the lunch snatcher.”