Baroness Young, the Conservative former leader of the Lords, wants peers to back a motion to quash the order legalising sales of the emergency contraceptive to the over 16's.
But the move has angered the Department of Health, who called it a retrograde step.
"It will be a major step backwards and pharmacies would have to be altered immediately to stop the sales of a safe and effective emergency form of hormonal contraception," said a spokesman.
But even if the vote goes Baroness Young's way the emergency pill will still be available on presciption.
The Tories have long campaigned against over the counter sales of the emergency contraceptive, saying that the best place for it to be dispensed is in the GP's surgery.
GP's surgery
Shadow Health Secretary Dr Liam Fox, a former GP, said: "We believe that the safest, most appropriate and most sensitive environment in which to prescribe the Morning After Pill is in General Practice.
"We understand concerns about access to the medication. That is why would allow prescribing by practice nurses," he said.
Dr Hamish Meldrum deputy chair of the British Medical Association's GP committee, said it is preferable for the emergency contraceptive to be dispensed through general practice, but that some women preferred to go to a chemist.
He said he had to back anything that would reduce unwanted pregnancies.
"I will go along with it, if it is going to reduce the number of unwanted conceptions," he said.
Ann Furedi, from the British Pregnancy Advisory Service (BPAS), agreed that the emergency contraceptives could cut unwanted pregnancies.
"We believe that pharmacy sale of emergency contraception is likely to increase its use and may therefore decrease the number of unwanted pregnancies.
"BPAS strongly supports the reclassification of emergency contraception to allow the sale of Levonelle from pharmacies and believes that it would be detrimental to public health if the order is annulled in the House of Lords," she said. Lady Young, whose Motion comes up in the Lords on Monday, also led the campaign against the Bill to lower the gay age of consent to 16.
Peers backed her and the change in the law was rejected.
Althought it was eventually steam rollered through by the Government using the Parliament Act.
Lady Young also successfully led opposition to the Government's attempt to scrap Clause 28, which bans the promotion of homosexuality in schools.