Theresa May is to call for a crackdown on intimation in politics warning the country faces a "permanent coarsening and toxifying" of public debate unless steps are taken to address the problem.
The prime minister will urge politicians on all sides to stand up against bullying of parliamentary candidates as she announces the launch of a consultation to make intimidation of candidates and their campaigners an offence in electoral law.
In her speech marking the centenary of the women's right to vote, Mrs May will say no one should be threatened for daring "to express a political opinion".
The consultation follows an inquiry by the Committee on Standards in Public Life in the wake of last year's general election that found women, ethnic minority and gay candidates were disproportionately targeted in terms of the "scale, intensity and vitriol" of the abuse they received.
"In the 21st century it cannot be acceptable for any woman - or any person - to have to face threats and intimidation simply because she or he has dared to express a political opinion," Mrs May will say.
"We can all see this change happening and I know that many share my concern about it."
She will highlight the role social media and other forms of digital communication play in spreading abuse.
"In public life, and increasingly in private conversations too, it is becoming harder and harder to conduct any political discussion, on any issue, without it descending into tribalism and rancour," she will say.
"British democracy has always been robust and oppositional but a line is crossed when disagreement mutates into intimidation."
She will add: "It is time we asked ourselves seriously whether we really want it to be like this. Whether we are prepared to accept a permanent coarsening and toxifying of our public debate or whether, together, we will take a stand for decency, tolerance and respect."
In her proposals for reform of the electoral law, Mrs May will also will set out plans to remove the requirement for candidates for council elections to have their addresses published on the the ballot paper - bringing local elections into line with parliamentary elections.