A Leeds MP has told Parliament of the "horrifying story" of a 91-year-old constituent subjected to what he described as a "predatory marriage".
Labour MP Fabian Hamilton said that registrars need greater training and powers to act if they see signs a person does not have the mental capacity to marry.
He called on ministers to close the "marriage loopholes" which saw one of his constituents, who suffered with dementia, able to marry a man 20 years her junior without her family's knowledge.
The Leeds North East MP, proposing his Marriage and Civil Partnership Consent Bill, told the Commons that more "robust procedures" were needed to protect the vulnerable and said "smiling at the time" of the marriage did not necessarily mean consent was given.
Mr Hamilton told MPs he was prompted to bring in his bill, via a 10 minute rule motion, after hearing a story he could "hardly believe was possible in modern Britain" from constituent Daphne Franks.
Mrs Franks revealed to Mr Hamilton that her 91-year-old mother Joan Blass had married a man more than 20 years her junior, despite having advanced vascular dementia, one year before her death.
READ MORE: Leeds MP to highlight case of 91-year-old woman in call for change to marriage laws to protect people with dementia
The marriage meant the will Mrs Blass had drawn up, naming her two children as beneficiaries, was void and she died intestate, meaning her new husband automatically inherited her assets.
Mrs Blass, a widowed former teacher and journalist, had lived in a house in Mrs Franks’ garden in Gledhow, Leeds.
Mr Hamilton said: "When her daughter saw her shortly after her death she was still wearing her first husband's wedding ring, but it was three days after her mother's death that Daphne discovered that she had been married in a civil ceremony at Leeds Town Hall.
"Members of this House may imagine what a shock this discovery was to Daphne, her brother and to the rest of Joan's family."
Mr Hamilton told how the family spent more than £200,000 on legal fees trying to annul the marriage, but the "sadly deficient" marriage laws in this area prevented any success, he said.
He said: "It's not good enough for a registrar simply to say that because one of the participants in the marriage ceremony was smiling at the time, that meant consent was happily given."
He added: "This Bill will establish that marriage should no longer revoke a previous will in every case or indeed in any case.
"There should be better training for registrars to ensure robust procedures for safeguarding vulnerable individuals are put into place.
"The capacity to marriage should be established via a simple questionnaire to alert registrars that an assessment of capacity may be needed before the ceremony is carried out."
The Bill was listed for a second reading on January 25 but is unlikely to become law in its current form without Government support or sufficient parliamentary time.