After four years of considering evidence, the Director of Public Prosecutions has announced that no charges will be brought against members of the security forces in several key collusion cases - including the solicitor's 1989 murder.

The decision brings to a close the Stevens investigations that spanned almost two decades.

But the prospect of a public inquiry into the case remains - and Mr Finucane's family said yesterday's announcement underlines the need to explore the background of the murder.

In 2003, Lord Stevens - then Britain's most senior police officer - declared that collusion had taken place, with soldiers and police cooperating with loyalists in the Finucane killing and at least seven other murders.

But in a statement issued yesterday, DPP Sir Alasdair Fraser concluded that there is not enough evidence to bring 24 members of the security forces and a civilian police employee to trial.

Those individuals are believed to include Brigadier Gordon Kerr, who headed up a shadowy Army intelligence squad known as the Force Research Unit.

John Finucane, the murdered solicitor's youngest son, said his family was " outraged by the nature of this decision".

"This was a very weak decision," he said.

"It's very insulting to me as someone who lost my father and it has vindicated my family's decision not to put our trust in the criminal justice system.

"I don't accept it on human grounds as a victim and I don't accept it on legal grounds either," said Mr Finucane, who is also a solicitor.

"John Stevens confirmed collusion existed and he said one aspect was the wilful failure to keep records. I find it insulting that the lack of records is now the get-out clause for the people who implemented this policy.

"What this decision says very clearly is that anyone who has lost someone or has been injured by the state cannot expect it to be dealt with by the authorities.

"It fuels the paranoia and fuels the hurt of those who have lost loved ones through state actions."

Over the course of his investigations, which began in 1989, Lord Stevens established that an Army agent, Brian Nelson, and a police informer, William Stobie, were both involved in the plot to murder Mr Finucane at his north Belfast home in 1989. Both were members of the UDA.

A third loyalist, Ken Barrett, was recruited to become a police informer after admitting to RUC officers that he shot Mr Finucane. He was later jailed for the murder.

In investigating security force links to the murder, Lord Stevens said he found "the wilful failure to keep records, the absences of accountability, the withholding of intelligence and evidence, and the extreme of agents being involved in murder".

The Prosecution Service spent four years considering the files and had employed three QCs to give legal opinions on the material compiled by Stevens.

"In relation to collusion it should be noted that whilst there is or may be conduct which may be characterised as collusion, there is no offence of collusion known to the criminal law of Northern Ireland," the statement said.

The DPP concluded that none of the evidence submitted by the Stevens Inquiry could be brought to court.

As well as the Finucane murder, the DPP looked at the murder of Adam Lambert, a Protestant student killed with weapons supplied by Stobie.

He also examined the actions of security forces in handing weapons back to Stobie, a UDA quartermaster. One of the guns was supposed to have been deactivated by police but was then used in Aidan Wallace's murder in 1991 and the 1992 Ormeau bookies massacre.

Mark Sykes, who was wounded in that attack, said he was "livid" at the decision.

Relatives for Justice said the DPP's decision could be challenged in court.

Its director Mark Thompson said the inquiry into the Finucane murder should not proceed under the Inquiries Act.