The family of Daphne Caruana Galizia, the anti-corruption journalist killed by a car bomb in Malta in October 2017, have raised concerns about the impartiality of individuals appointed to lead a public inquiry into her death.

The Maltese government announced a wide-ranging inquiry late on Friday, six days before the expiry of a three-month deadline set by the Council of Europe.

The announcement came after a long campaign by the family, who have been calling for greater scrutiny into what they claim is a lack of accountability for criminal actions and political corruption in Europe’s smallest member state.

Caruana Galizia’s family have requested an urgent meeting with the prime minister, Joseph Muscat, saying: “The board [of inquiry] will be unfit for purpose if the public has reason to doubt any of its wider members’ independence or impartiality.”

Three men are awaiting trial for allegedly planting the bomb that killed Caruana Galizia, but the police investigation to uncover who ordered her assassination has stalled.

The terms of inquiry set out in a statement released by the government range from determining whether the state could have prevented the killing, to whether criminal law provisions are sufficient to prevent a culture of impunity. The commission meets in public, but its members can decide to hear some witnesses in private. The government says it expects the inquiry to take nine months.

The commission will be chaired by retired judge Michael Mallia, and its two other members are a litigator and professor of law at the university of Malta and a former director of forensic science laboratories at the Malta police department.

“Given the gravity of its purpose and its mandate to investigate state institutions,” the family said, “justice demands that the board’s wider members have no financial or political links to the current political administration”.

It is understood the family support the choice of Mallia as chair but have concerns about the impartiality of the other two commission members.

Caruana Galizia’s son, Paul, said on Twitter on Saturday morning there were “serious problems with regard to the members of the Board of Inquiry announced last night”.

Serious problems with regard to the members of the Board of Inquiry announced last night. One represents clients my mother investigated for money laundering. Another depends on the Prime Minister for his livelihood. These clear conflicts will poison the inquiry’s work. https://t.co/3hP4MBdCah — Andrew Caruana Galizia (@acaruanagalizia) September 21, 2019

According to reports published by Maltese news outlets, one of the members, law professor and litigator Ian Refalo, has represented clients investigated by Caruana Galizia for corruption.

“The establishment of a public inquiry is long overdue, and is an essential step towards justice for the assassination of Daphne Caruana Galizia,” said Rebecca Vincent, UK bureau director of journalists’ campaign group RSF.

“But a public inquiry that lacks independence and impartiality will fool no one – and the goal remains full justice for this heinous assassination. We will remain vigilant and scrutinise the composition and actions of the board of inquiry, and act to hold the Maltese government to account.”

Last year the Council of Europe appointed a special rapporteur, Pieter Omtzigt, to investigate the killing. He produced a report which led to a vote by the 47-country human rights organisation, giving Malta a three-month deadline to launch an independent inquiry.

Omtzigt welcomed the announcement, adding: “I will now examine closely the terms of reference of the inquiry ... as well as its scope, powers and membership, before commenting further. Any such exercise must be fully independent, and its members’ impartiality beyond question.”

In its announcement, the Maltese government said it was important that the public inquiry should not “undermine investigations and/or criminal proceedings which are pending in this case,” and that it had engaged in technical discussions with officials of the Council of Europe to avoid any such risk.

Muscat was a frequent target of the journalist’s investigations. Caruana Galizia came under huge political pressure after revealing that members of his administration had set up secretive offshore companies shortly after entering government.