Image copyright David Swanson/ Philadelphia Inquirer Image caption Mr Bobbitt (bottom left) lived with the couple, but is now back on the streets

A homeless man is suing a US couple who raised more than $400,000 (£307,000) to help him, alleging they used the funds as their own "piggy bank".

Johnny Bobbitt went viral last year when he gave his last $20 to Kate McClure when her car ran out of petrol.

Ms McClure and her boyfriend Mark D'Amico started an online fundraiser for him, which drew contributions from over 14,000 donors.

The legal action - alleging fraud and conspiracy - was filed on Tuesday.

Lawyers for the 35-year-old wrote in documents filed in Mount Holly - a New Jersey suburb of Philadelphia - that the couple had used the GoFundMe account they set up for Mr Bobbitt "to fund a lifestyle that they could not otherwise afford".

In recent interviews, Mr Bobbitt said Ms McClure, 28, and Mr D'Amico, 39, had recently paid for trips to Las Vegas and Florida, and a new BMW.

Mr D'Amico works as a carpenter and Ms McClure is a receptionist for the New Jersey Department of Transportation, according to local media.

A judge is set to hear the case on Thursday.

A representative for the civil court told the BBC the couple do not have an attorney listed on record.

Last week, Ms McClure told the Philadelphia Inquirer she felt frustrated and betrayed, and that she still wished to help Mr Bobbitt.

"I don't want to lose my job over this," she tearfully told the newspaper.

After wildly surpassing their original fundraising goal of $10,000, the couple had told their online supporters the money would go to two financial trusts for Mr Bobbitt, as well as a lawyer and a financial adviser to help him manage all the money.

They gave him clothing, allowed him to park his new camper outside their home, but reportedly later asked him to leave.

Mr Bobbitt says the couple sold his camper, gambled away some of his money, and have declined to provide him with any financial records.

Image copyright David Swanson/ Philadelphia Inquirer Image caption Mr Bobbitt, pictured earlier in August, has continued using drugs

The couple claims he once blew $25,000 on drugs in just 13 days.

"Every dollar he ever touched was used for drugs," Mr D'Amico told NBC in a nationally televised interview on Monday.

He added that he would be "absolutely" willing to allow an accountant to review financial statements to determine how the money was used, and what remains.

Mr Bobbitt, a US Marine veteran, is now back living on the streets with his younger brother.

In an interview with the Inquirer, he said begging for change to buy drugs was better than trying to get money from Mr D'Amico and Ms McClure.

Jacqueline Promislo, a lawyer for Mr Bobbitt, told the BBC she took the case pro bono to make sure he would be able to benefit from the charity of thousands of people "so he could not be homeless again".

Ms Promislo said her client estimates the couple did spend about $75,000 on his care.

During the NBC interview Mr D'Amico said about $150,000 remains.

Ms Promislo said her office hoped to avoid going to court.

"It's not the couple's money to decide where it goes," she said.

"Every single person I have heard from, that has emailed or called, is extremely upset and very much want Johnny Bobbitt to receive the money they gave to him."

A spokesman for GoFundMe says it "is looking into the claims of misuse".

"We will work to ensure that Johnny receives the help he deserves and that the donors' intentions are honoured," the spokesman added.