The Australian government has spent more than $4.5 million in its attempt to expel a Sri Lankan family of four, including two children born in Australia, from the country, BuzzFeed news reported.

That figure, from September 2019, is likely to have sharply escalated over the past four months as the married couple and their two young daughters have been held on an island far from the Australian mainland while they fight deportation.

The "Biloela family" — a Tamil family who spent years in the regional Queensland town of Biloela before being taken into immigration detention — attracted widespread protest and global media attention when the Australian government moved to deport them last August.

Since late August, Nadesalingam (known as Nades), Priya and their two Australian-born daughters, Kopika and Tharunicaa, have been the only people held on Christmas Island, an external territory of Australia.

Australian Border Force officers and employees from private contractor Serco took them from their home in Biloela in a dawn raid in March 2018, when their youngest daughter was seven months old. They spent over a year in detention in Melbourne, as they fought for protection visas, before coming nail-bitingly close to deportation in August 2019.

An last minute injunction issued by the Federal Court granted them temporary reprieve from deportation. A case looking at whether Tharunicaa, the younger daughter, is entitled to a protection visa is ongoing.

Biloela residents have called for the family to return to Queensland under the banner of the Home To Bilo campaign. Thousands have come out to protest their detention. But the government has held firm to its hard line: strong borders come first.

In the meantime, the government moved the family from Melbourne to Christmas Island, which sits more than 3,000km off the mainland’s west coast and is closer to Indonesia.

The family’s detention has cost Australian taxpayers $2.5 million, according to new figures provided by the Department of Home Affairs to the Senate. The figures were current at Sept. 16, 2019 — which means they are likely to be much higher today. The government has spent another $1.1 million on travel and transportation. The ongoing legal fight has cost the government at least $300,000. And a further $600,000 has gone to other expenses, including costs for staff who removed the family to Christmas Island.

Christmas Island’s detention centre, which the government reopened in February 2019, cost almost $27 million even before the Sri Lankan family, now its only detainees, arrived. For the six months before they arrived, it sat empty — but was staffed by 125 people.

The Department of Home Affairs did not clarify how it calculated the $2.5 million cost of detention, and whether that included the ongoing costs of the contract with Serco to operate the Christmas Island centre.

The government had claimed that the family was transferred from the mainland to Christmas Island on the advice of the Australian Border Force commissioner, for the safety of both the family and the officers guarding them. But there is no written record of that advice, the Guardian has reported.

The family’s lawyer has complained that the move to Christmas Island has obstructed her access to her clients.

Labor senator Kristina Keneally requested the figures after home affairs minister Peter Dutton said in a radio interview the family had cost taxpayers "literally millions of dollars" because advocates "armed with pro bono lawyers" fought for them.

Dutton described the two young girls as "anchor babies" in the September interview, accusing the couple of "trying to leverage a migration outcome based on the children". He said it was "frustrating" the couple had them after being told they were not going to stay in Australia.

Nades and Priya came to Australia separately by boat in 2012 and 2013. They met and married and then had their daughters. They settled in Biloela, population 6,000, where Nades worked in an abattoir and volunteered at St Vincent de Paul.

Before the family was taken into detention their protection claims had been rejected and their further appeals were unsuccessful. Most recently, the High Court dismissed an application to hear the case in May 2019.