The crown prosecution service (CPS) has cleared Peter Hain of wrongdoing over donations to his deputy leadership bid.
Mr Hain quit his job as work and pensions secretary while the investigation was being conducted, but the CPS say there is not enough evidence to charge him with any wrongdoing.
Mr Hain said he had spent ten months "in limbo" while the case was being investigated, but held out the prospect of rejoining the government.
"I stepped down from the government to clear my name and now I'm pleased I have done so," he told the BBC.
"It is for the prime minister to decide whether he wants me to assist in the way that I have done in the past. I think there's big, big jobs to do to make sure that the country emerges from the global financial crisis and I think we're doing a good job trying to do that."
Downing Street offered strong hints a return to the Cabinet was possible.
Earlier today, the prime minister's spokesman said: "We obviously welcome the fact that Peter Hain has been cleared in this matter. Peter has been a great servant of the Labour party and has much to offer in the future."
Meanwhile, Stephen O'Doherty, reviewing lawyer from the CPS special crime division released a statement on the investigation.
"The evidence in this case shows that Mr Hain's campaign was run through an organisation named Hain4Labour which was made up of members of the Labour party," he said.
"That organisation had its own bank account and the funds for Mr Hain's campaign were solicited for that account and cheques donated were made out to that account.
"Those were all characteristics of a 'members association' as defined in the [Political Parties, Elections and Referendums] Act. Mr Hain was not a signatory to that account and did not direct where funds should be spent."
Under the Political Parties Act, Mr Hain would have had to have been a 'person responsible for dealing with donations to the association' to have committed a criminal offence.
Mr Hain had told the Electoral Commission he received £82,000 for the campaign, which was eventually won by Harriet Harman.
But further undeclared donations then came to light from City and business figures, as well as a £10,000 sum from the GMB union.
There were also concerns over a thinktank, the Progressive Policies Forum (PPF), which was said to have channelled funds to the campaign.
The police were keen to justify their investigation today.
A spokesman said: "As with any police investigation we have followed the evidence in order to prove or disprove whether a crime has been committed.
"At every stage this investigation has been approached in a timely, professional, thorough and proportionate manner with the full inclusion of the CPS throughout."