High Street chemist Boots sent a legal letter to the pregnancy charity which launched a campaign calling on the chain to cut the price of emergency contraception, the charity has said.
The British Pregnancy Advisory Service (BPAS) said Boots accused it of the "facilitation and tacit encouragement of personal abuse" that "caused immense personal distress" to senior Boots executives.
Boots described emails and comments on social media as a "torrent of personal abuse" against their employees, according to the charity.
But BPAS said Boots failed to provide any evidence of abuse sent through the campaign and "comprehensively misrepresented" messages from members of the public.
In a statement, published by Sky News, Boots said: "As a responsible employer, we actively seek to protect our colleagues from abuse and harassment.
"In our legal letter to BPAS we made it very clear that we welcome the debate on the provision of EHC (emergency hormonal contraception), and respect their right to raise this issue with us.
"We asked them simply to remove personal email details from their campaign widget and to agree not to encourage personal abuse of our people. We provided examples of where our employees have received abuse by email and social media in response to BPAS's campaign.
"BPAS have not yet agreed to do this and we will continue to ask that they agree to our simple request, which was made only to protect the interests of our employees.
"We hope to receive a constructive response from BPAS, and do not wish to comment further at this time."
The legal letter came after Boots said it was "truly sorry" for the way it responded to a campaign calling on it to reduce the price tag on the emergency contraceptive.
The chain faced criticism in July after refusing to reduce the cost of the morning-after pill over fears it could incentivise its use.
At the time, Boots said its price tag was based on the cost of the medicine and the consultation the pharmacists carries out with women but it was "committed" to finding less expensive versions of the tablet.
On Thursday, Boots announced that 38 stores are now offering a new, less expensive generic version of EHC (Levonorgestrel) at a cost of £15.99, adding that it will be offered across all stores in October.
A Boots spokesman said: "We're committed to listening to our customers on this important matter, and have been working hard to establish a sustainable supply of this medicine so we can offer this as part of our EHC service nationally across all 2,500 of our stores.
"We continue to believe that the best way to increase access of EHC is for a free NHS service to be made available to all women for the provision of EHC in England, as it is in Scotland and Wales."