An Asian police officer who claims his colleagues framed him for theft after he sued his force for racism is to have his criminal conviction quashed today.

Sultan Alam was jailed for 18 months after starting legal action against Cleveland Police in 1993. Sources told the Guardian that the Crown Prosecution Service (CPS) will announce today that it will not contest his appeal against conviction. This will mean that the court of appeal is near certain to clear his name.

Alam served as a constable and officially made a claim of racism against the Cleveland force in 1993. Months later he was charged with handling stolen car parts, for which he was convicted at Teesside crown court in 1996.

He served nine months of his sentence and was dismissed in 1997 in disgrace from the force after a 13-year career.

He has always maintained that he was framed after he started to sue the force for racial discrimination following a series of incidents, culminating in a Ku Klux Klan poster being left on his desk.

In 1999 an investigation by an outside force, Northumbria, into his claims began and was codenamed Operation Granite. It lasted two and a half years.

The CPS subsequently decided that four officers should be charged with criminal offences over allegedly framing him. All were cleared in 2004, but one later admitted two offences arising from the case at a disciplinary hearing. Three have since left the force.

The strain of his ordeal led to the break-up of Alam's first marriage. On release from prison he first made a living by driving a taxi and now runs a mobile phone shop.

One of the key parts of his appeal was that material that could have led the jury at his original trial to acquit him was kept from his defence lawyers.

Alam was denied help by the Police Federation, which was found to have racially discriminated against him by an employment tribunal last year. The federation had refused to help him take legal action to clear his name.

The tribunal ruled there was overwhelming evidence that Alam was racially discriminated against and victimised. It also found that documents had been destroyed by a federation official in an attempt to thwart him.

Alam had twice sought help from the federation to clear his name by funding an appeal against his conviction after new evidence came to light. It refused, but had paid for the legal defence of the four officers who stood trial charged with framing him.

The case will be an embarrassment for the police service, which has been dogged for years by allegations and findings of racism.

The Cleveland force will come under scrutiny after today's announcement by the CPS, as to whether they did enough to correct the injustice Alam suffered.

Ali Dizaei, acting president of the National Black Police Association, said: "We request an immediate intervention by the Independent Police Complaints Commission to review this case in its entirety to find out how Mr Alam faced these horrible charges. This sort of case has happened before to black officers."

Cleveland police refused to answer any questions about the 14-year saga, including whether they had ever admitted failing Alam.

The former officer and his solicitor declined to comment ahead of the court of appeal's judgment, which is expected today.