The British authorities said her action has cost the National Health Scheme (NHS) up to £200,000, while she is allegedly working illegally as an Avon Lady salesperson in Britain.

Mrs. Ayelabola applied for a six-month visitor’s visa soon after discovering she was pregnant and travelled to the UK, without her husband, to visit her three sisters.

She gave birth to two boys and three girls in April after a complex Caesarean section and remained in hospital for almost two weeks, paid for by the taxpayer.

Within days of returning to her sister’s flat in Poplar, East London, she began distributing catalogues and selling Avon’s make-up, perfume and beauty products.

But, under the terms of her visa, which expired last month, she is unable to work in the UK or claim benefits.

She is now fighting to remain in the country.

Yesterday, a neighbour said: “She has dropped at least two Avon booklets through the door in the past couple of months. I’m sure she has visited other homes in surrounding streets.

She’s definitely working for Avon because I bought something from her last month. She never let on that she was not allowed to work in this country.”

A Home Office spokesman also said last night: “The UK Border Agency will thoroughly investigate any reports of anyone breaking the terms of their visa.”

Mrs. Ayelabola is registered as a full-time mother on her children’s birth certificates.

She says she was unaware she would have as many as five babies, when she arrived in Britain late last year.

The multiple births are likely to be a result of double doses of fertility drug Clomid, which she took for eight times longer than recommended after buying the pills over the counter in Lagos.

The total bill to the taxpayer for Mrs. Ayelabola’s care is expected to reach £200,000.

Foreign nationals should be charged for the full cost of their treatment, but Mrs. Ayelabola is not able to pay.

The five babies, who were born prematurely at 32 weeks, were treated in a special-care unit, where the cost of a week’s stay for the family would be £35,000 alone.

The case has once again raised the issue of ‘health tourism’, in which foreigners come to take advantage of Britain’s state-funded health system.

It is estimated to cost the NHS £200 million a year.

Mrs. Ayelabola was treated at Homerton Hospital in Hackney, East London.

Andrew Boff, a Hackney resident and Conservative member of the Greater London Authority, said: “You can’t refuse to give someone treatment once they’re in the country, as we’re talking about human life.

“But, what this case does point out is that this country does not have a good immigration policy.

“It does need to be stricter in its application. Our health system should be for those who live in the UK.

“It can’t be open to anybody who comes in speculatively. That’s because UK people fund it.

“It should be a requirement for anyone coming in that they have an adequate travel insurance policy, to prevent such occurrences in future.’

Mrs. Ayelabola has applied for an extension to her visa as she claims the children – Tayseel and Samir (the boys) and Aqeelah, Binish and Zara (the girls) – are still too frail to travel.

She said in an interview: “I had already had miscarriages and couldn’t bear the stress another pregnancy would cause. I thought I would stand a much better chance of avoiding another miscarriage in a calmer place with friends and family.”

Her 37-year-old husband, Ohi Ilanbare, a civil engineer, remains in Nigeria.

However, the children do not have an automatic right to British citizenship, despite being born in the UK.

To qualify, they would need at least one parent who is British, or who has indefinite leave to remain in the country.

An Avon spokesman said the firm would investigate how Mrs. Ayelabola became a saleswoman for the brand. She was unavailable to comment.