Almost 8,000 patients were treated on mixed-sex NHS wards in the 12 months to March, figures show.
New NHS England data analysed by the Liberal Democrats shows a rise over the past two years in the number of breaches of NHS rules that say men and women should be treated on different wards.
Overall, 7,771 patients stayed in mixed-sex wards between April 2016 and the start of March 2017.
This compares to 5,309 in 2015/2016 and 2,655 in 2014/2015, the analysis showed.
Liberal Democrat health spokesman Norman Lamb said: "Far from being eliminated, the number of patients being forced to stay in single-sex accommodation has tripled since this Conservative government came to power.
"This is a major embarrassment for Jeremy Hunt and yet another sign of the impossible pressure our NHS is under.
"The progress we made in reducing mixed-sex wards during the coalition government is now completely unravelling.
"Men and women should never be forced to share hospital wards in a modern health service. It is an affront to basic human dignity.
"The Conservatives should clarify to the public whether they will again include this failed commitment in their manifesto and how they expect to meet it.
"This election is a chance to change the direction of our country and end this Conservative government's disgraceful underfunding of the NHS."