By Kirstin Ridley

LONDON (Reuters) - Britain's Serious Fraud Office (SFO) is working with French authorities in its investigation into alleged fraud, bribery and corruption at European aerospace group Airbus <AIR.PA> and expects to proceed "fairly quickly", its head said on Wednesday.

The SFO launched a criminal inquiry in August into Airbus' use of third-party agents to win commercial jet sales after the company's compliance teams informed Britain's export credit agency, which arranges credit guarantees for overseas sales, of inaccuracies.

"We have spoken to the French and continue to do so," SFO head David Green told Reuters. He declined to say whether the agency was also in contact with the U.S. Department of Justice, saying only it would "speak to any interested party".

The case involves discrepancies over the amount of agents' fees disclosed in applications for export support, or missing names of third parties, in some cases dating back several years, two people familiar with the matter have said.

Airbus has said it is cooperating with inquiries but Green said it was too early to say whether Airbus would qualify for any offer of a Deferred Prosecution Agreement (DPA), in which a company accounts for alleged offending to a criminal court and, if a judge agrees, can settle the case with a fine.

BIG CASES TO WRAP UP

Most companies investigated by the SFO say they are fully cooperating with the authorities, although Green said this was not always strictly accurate.

But he agreed that Britain's Tesco <TSCO.L> was cooperating with a criminal inquiry into accounting practices, launched after the supermarket chain said it overstated half year profits in August 2014 by about 260 million pounds ($320 million).

Three former Tesco executives were charged with fraud and false accounting in September and have since denied the allegations, but the wider investigation is continuing. The SFO would decide "in the fullness of time" if a DPA were appropriate in that case, Green said.

Since Green took charge in 2012, the SFO has been restructured and re-focused to rebuild confidence in its crime-fighting abilities. He aims to wrap up the big cases kicked off on his watch by the time he steps down in April 2018.

The SFO's success in securing three convictions of former traders for Libor interest rate rigging in July, bringing its convictions in the high-profile case to five, came after heavy criticism for its handling of cases such as the collapse of the corruption trial of businessman Victor Dahdaleh in 2013 and that of six brokers acquitted of alleged Libor fixing.

The agency will come under scrutiny again next year when another two former Libor traders face a re-trial after a jury was unable to reach a verdict. Six more former traders face a separate trial over Euribor rigging charges next year.

Meanwhile, separate inquiries into how Barclays secured a multi-billion pound emergency financing from Qatari investors in 2008 and the possible manipulation of Bank of England liquidity auctions in the same year are on track to be completed this year, Green said.

A lawyer for the SFO said in May that the agency expected to decide by early 2017 whether to bring any criminal charges in the Barclays case - a drawn-out investigation that Green said proved "the resolve" of the SFO.

($1 = 0.8042 pounds)

(Editing by Alexander Smith)