The government is being urged to address the continuing “blatant sexism” of marriage certificates, which currently ask for the names and professions of the fathers of the bride, and groom, but not that of the mothers.

Pushed by campaigners last year, the prime minister promised he would address the issue, which he acknowledged did “not reflect modern Britain”. But 12 months on no action has been taken.

The Green party MP Caroline Lucas reopened the debate on Monday, tabling an early day motion urging David Cameron to reform the certificates, which have not changed since the beginning of the reign of Queen Victoria.

“The government must act now to correct the blatant sexism of only having fathers’ details on marriage certificates,” said Lucas. “The prime minister has accepted that marriage certificates are discriminatory – yet his government has been unforgivably slow to act on this issue. It’s high time we end this institutional inequality and update marriage certificates to be fit for modern society.”

When called to address the issue last year, Cameron said he would speak to the Home Office to see how the matter could be addressed. “The content of marriage registers in England and Wales has not changed since the beginning of Queen Victoria’s reign ... and it’s high time the system was updated. So I have asked the Home Office to look at how we can address this,” he said.

Cameron made the comments following a public campaign run by Ailsa Burkimsher Sadler on Change.org which gathered 70,000 signatures, while a previous motion led by Lucas garnered the support of more than 100 MPs.

Pleased to announce on @BBCWomansHour campaign of direct action to get #MothersOnMarriageCerts - just write them in! http://t.co/icas59DI6o — Caroline Lucas (@CarolineLucas) October 12, 2015

A new petition from Rhiannan Sullivan [], the child of a single mother, has been launched by Care2, an activist social networking site, to keep the pressure on the prime minister. By Monday lunchtime it had more than 20,000 signatures.

Sullivan said she was saddened and shocked that the person who raised her would not have her name or profession noted. “My father has not been a major part of my life since I was a small child yet when it comes to signing our marriage certificates there is space for his name and profession on the form, but not my mother’s,” she said.

“I had no idea this archaic practice still existed. The fact that the one person who has not only raised me, but has inspired me throughout my whole life, will not be registered or named on such an important and legal document is ridiculous.”

Members of the public are also using social media to put pressure on the government to change marriage certificates using the hashtag #MothersOnMarriageCerts and are being asked to tell their MPs to sign the motion.

Lucas is also calling for couples getting married to take their own direct action. “Pleased to announce on @BBCWomansHour campaign of direct action to get #MothersOnMarriageCerts – just write them in!” she tweeted.

Downing Street and the Home Office did not respond to a request to comment on Lucas’s early day motion by the time of publication.