THERESA May is set to warn that online abuse and intimidation is threatening the UK's democracy, as she hails the "heroism" of the suffragettes who won the vote for women 100 years ago.
On the centenary of the 1918 Representation of the People Act today, which granted the vote to many women aged over 30, Mrs May will set out plans to counter the online "bitterness and aggression" which is deterring many from engaging in political debate.
In a speech in Manchester to mark the 100-year milestone, the Prime Minister will announce plans for a Law Commission review of legislation to ensure that actions which are illegal offline are also illegal online.
And she will pledge to establish a new annual internet safety transparency report, to provide data on how social media companies are dealing with abusive material.
Mrs May will endorse the recommendations of a report into intimidation produced last year by the Committee on Standards in Public Life, which called for legislation to shift the balance of liability for illegal content to the social media companies.
A social media code of practice will be released later this year, while the Government will publish its Internet Safety Strategy in the spring.
The Prime Minister is expected to say: "As we remember the heroic campaigners of the past, who fought to include the voices of all citizens in our public debate, we should consider what values and principles guide our conduct of that debate today."
And she will add: "While there is much to celebrate, I worry that our public debate today is coarsening.
"That for some it is becoming harder to disagree, without also demeaning opposing viewpoints in the process."
Abuse of political candidates and representatives is often targeted at women - as well as gay people and members of ethnic minorities - online, she will say.
"In the face of what is a threat to our democracy, I believe that all of us - individuals, governments, and media old and new - must accept our responsibility to help sustain a genuinely pluralist public debate for the future," Mrs May will say.
"The social media companies themselves must now step up and set out how they will respond."
Reflecting on the centenary Mrs May is expected to say: "As the woman at the head of our country's government, a century after my grandmothers were first given the right to vote, my mission is clear.
"To build that better future for all our people, a country that works for everyone, and a democracy where every voice is heard."
Mrs May will later address a reception in Parliament to launch a year-long Vote 100 programme of events to celebrate a century of female suffrage.
All female MPs past and present have been invited, in what is expected to be the largest gathering of the UK's women politicians ever organised.
The north's Department for Communities is holding a series of events throughout the year to mark the change in voting rights.
Female MLAs launched the centenary commemorations at an event at Parliament Buildings in Belfast last night.
