Since been contacted by 600 people who claim to have been targeted

Ms Alouane lost £150,000 to her Tunisian former husband after break up

The Home Office has been accused of failing to deport hundreds of foreign fraudsters who con Britons into marriage, to get a UK visa and to plunder their finances.

Victims of immigration marriage fraud have told The Mail on Sunday that Theresa May's department is a 'shambles' and is not doing enough to tackle the problem.

Not one alleged scammer has been deported or prosecuted despite an estimated 1,000 cases of marriage fraud being reported in the past year alone.

Kim Sow, 58, has been calling for action since her Senegalese husband Laye walked out on her in 2013 after obtaining his British citizenship, leaving her £50,000 out of pocket

A new Home Office intelligence unit has been launched to combat the growing problem, but angry victims want the Government to 'wake up' and start investigating cases.

'We are seeing about 20 cases a week but no one is being prosecuted, no one deported,' said Kim Sow, of victim support group Immigration Marriage Fraud UK.

'These are long cons. The authorities need to realise it's not just about getting British citizenship, it's also about getting as many material assets as they can.'

Mrs Sow, 58, has been calling for action since her Senegalese husband Laye walked out on her in 2013 after obtaining his British citizenship, leaving her £50,000 out of pocket.

Working as a promoter within the World Music scene, she met musician Laye at a London nightclub in May 2007. He told her he was a widower supporting three young children in Senegal. He even showed her a death certificate for his late wife and three birth certificates for his children.

'He was a talented, intelligent and good-looking man, and seemed religious and humble. He seemed the perfect match for me,' she said.

'I thought it was love in his eyes, but it was pound signs.'

The couple had an Islamic ceremony in Dakar, Senegal, in December 2007, and married again at Kingston-upon-Thames Register Office in June 2008. Mrs Sow bought a large Victorian home in Dover, in preparation for her becoming step-mother to his children.

Immigration Minister James Brokenshire last night insisted the Home Office was tightening the rules on marrying foreign partners

After three years he won British citizenship. But then a shocked Mrs Sow found out that his wife was still alive, and found Facebook messages from Laye to scores of other women he was targeting on dating websites.

He was also expecting a child with a British woman he'd been seeing behind her back. It later emerged he was wanted by immigration police in The Netherlands over an alleged marriage to a Dutch woman in 2002.

Police have begun an investigation into Laye for bigamy, fraud and associated crimes. But it is unclear if he is still in Britain, and he did not respond to requests for comment.

Following the break-up, Mrs Sow joined Immigration Fraud UK which has been founded in 2013 by Delene Alouane following problems with her Tunisian ex-husband.

They have since been contacted by 600 people (70 per cent women and 30 per cent men) who say they have been targeted and duped into marriage by immigrants seeking a visa.

After marriage, they apply to settle in Britain with their UK spouse, before dumping them when they are granted the right to remain here indefinitely, or acquire citizenship.

It is common for the fraudster to claim half of their UK partner's home by having their name added to the property by the Land Registry without their spouse's knowledge.

In many cases, they also rack up five-figure credit card bills and loans secured against their unsuspecting partner's property.

Immigration Minister James Brokenshire last night insisted the Home Office was tightening the rules on marrying foreign partners.