"Donations dried up a long time ago. At times the story comes into the news a few kind people send in a quid or two but there is nothing of any real value," the source said.
According to Metro UK, in the first months of the investigations after Maddie disappeared in May 2007, £1.8 million ($3.5m) was donated to the fund, £64,000 ($126,344) of which was from merchandise sales.
However, financial support for the search of Maddie is expected to run out by the end of the month as The McCanns wait to find out if a request for fresh cash from the UK Home Office will be made.
The Madeleine Fund, officially called Leaving No Stone Unturned, which was launched shortly after she went missing, has a sum of £750,000 ($1.48m) left in the pot, but this could soon be wiped out.
If the police search is shelved, the McCanns will dip into the fund to pay for their own private investigators.
A large chunk of it ($843,440) may also be needed to cover costs of an ongoing bitter legal battle against a former Portuguese police chief Goncalo Amaral. He accused the McCann's of being involved in their daughter's accidental death and covering up — false claims over which the couple sued him for libel.
So far, police have spent more than $39.28m searching for Maddie, who would have celebrated her 15th birthday in May this year. The last handout from the government of $293,500 was given at the start of April.
A family member told the Daily Mail: "We have to wait to see what the Home Office decide about the Grange operation."
However, the publication reported that a Home Office spokesperson said that to date, no request has been received from the Metropolitan Police Service to extend funding for Operation Grange beyond the end of September 2018.
In 2011, Scotland Yard launched its own review, named Operation Grange, into the case.
"Before we would even consider an application from the Met Police to continue its Operation Grange inquiry, we need to know what work is left to be done and how much is would cost," a spokesperson said.
Despite the global search, there has been no significant clues as to what could have happened to Maddie.
Maddie was three when she disappeared from a holiday apartment in the Algarve region of Portugal while her parents dined with friends nearby. She had been sleeping in the same room as her younger brother and sister.
Her twin siblings Sean and Amelie have just turned 13.
Kate and Gerry have never given up hope that their daughter could still be found alive.
Gerry, a renowned heart doctor will be giving an interview on BBC's Radio 4 programme Pearl: Two fathers Two Daughters discussing his heartache and mental health issues over the loss of his daughter.
It will be broadcast on September 29, just one day before the search for Maddie could continue or be axed.
