Theresa May has promised that a Conservative government will tackle the "five giant challenges" facing Britain over the coming decade, as she launched the party's manifesto for the June 8 general election.

In a foreword to the document, being launched in the Tory target seat of Halifax in West Yorkshire, the Prime Minister warns that the next five years will be the most challenging period the UK has faced for 60 years.

As well as the massive task of pulling the UK out of the European Union, the government elected next month will need to deal with the challenges of building a strong economy, tackling social division, meeting the pressures of an ageing society and making sure that Britain responds to the upheavals caused by fast-changing technology, she said.

"The next five years are the most challenging that Britain has faced in my lifetime. Brexit will define us: our place in the world, our economic security and our future prosperity," said Mrs May.

"So now more than ever, Britain needs a strong and stable government to get the best Brexit deal for our country and its people.

"Now more than ever, Britain needs strong and stable leadership to make the most of the opportunities Brexit brings for hard-working families.

"Now more than ever, Britain needs a clear plan.

"This manifesto - Forward, Together: Our Plan for a Stronger Britain and a Prosperous Future - will meet the great challenges of our time, beyond Brexit.

"With this plan and with a strong hand through Brexit, we will build a stronger, fairer, more prosperous Britain for all of us."

Unveiling what she termed "my manifesto for Britain's future", Mrs May said it was: "A manifesto to see us through Brexit and beyond, a plan for a stronger, fairer, more prosperous Britain, a plan to seize the opportunities ahead and to build a country that our children and grandchildren are proud to call home."

She said the document set out "a vision for Britain, a portrait of the kind of country I want this nation to be after Brexit as we chart our own way in the world".

Mrs May warned that if the upcoming Brexit talks failed to deliver a good deal, "the consequences for Britain and for the economic security of ordinary working people will be dire".

But she said: "If we succeed, the opportunities ahead of us are great."

She promised that her government would be "relentless in tackling burning injustices" and would govern for "mainstream Britain".

"With the right Brexit, my mainstream government will deliver for mainstream Britain," she said.