The group, along with relationships charity One Plus One, has set up a website aimed at correcting some of the common misconceptions behind the 'common law' concept. But many people only discover the real situation the hard way.

BBC News Online spoke to one woman left completely unprotected after her partner's death. Their names have been changed at her request.

Emily became involved with a co-worker, Nic, in 1992. They began living together the following year.

Nic was married when they began seeing each other and never got a divorce, as he feared this would mean his wife would leave London along with his two children, who are now 20 and 18.

In 2002, Emily bought a house in Italy. Nic stayed there with power of attorney to take care of some of the legal details while Emily returned to London to look after the finance.

"I had romantically, and misguidedly, put the house into joint names although I was the purchaser," Emily said.

"The day after we bought it, Nic died."

No rights

Emily knew she was not the next of kin and that she therefore had no legal rights. "It was something about which we argued as he didn't believe me."

Nic, who was 48 years old, did not leave a will, meaning his wife inherited a �220,000 package from his employers, his �8,000-per-year civil service pension and maintenance for her children until they leave higher education.

"I am sure the sum he left was largely untouched from the date of redundancy because I paid the household bills and expenses, thus allowing him to keep paying ... for the children," Emily said.

A fight began over the house in Italy as, since it was partly in his name, Nic's wife could claim half of it. Emily says she has been assured his wife will not pursue that claim, although she has not received the signed waiver formalising that promise.

I feel I have been written out of history 'Emily'

She says the worst aspect of the situation is that Nic's wishes are not being respected. He had wanted his money split evenly between her and his two children, she said.

"He made it perfectly clear to his friends and the people around him, but he never wrote it down.

"He ended up a bit like a rabbit caught in headlights and did nothing."

Emily says she and Nic could have avoided "an immense amount" of hassle if they had been more practical, "but you just don't think this sort of thing is going to happen". As a result, she was left with little legal backing to her 10-year relationship.

"I feel I have been written out of history," she said.