The fraud squad's investigation into Soma Oil & Gas set it back almost £60,000, City A.M. has learned.
Answering a Freedom of Information request, the Serious Fraud Office (SFO) revealed it spent £59,912 on its investigation into the oil company, which opened in July 2015, following allegations of bribery and corruption.
The figure does not include permanent staffing costs, as the SFO does not divide these amounts on a case-by-case basis for most investigations.
"The SFO has concluded, based on the information and material we have obtained, that there is insufficient evidence to provide a realistic prospect of conviction," the fraud watchdog said when it announced the end of the probe, although it added there had been "reasonable grounds" to suspect wrongdoing.
Soma is a UK company chaired by former Tory party leader Lord Howard which was established in 2013 to explore for oil in Somalia.
At the time the case was closed, the firm said it welcomed the end of the investigation and "looks forward to executing its plan to further explore what is believed to be very considerable hydrocarbon potential offshore Somalia in 2017 and beyond".
However, the case did get some time in court, after the company took legal action against the fraud squad in a bid to make them drop the probe.
The case was ultimately not decided in the company's favour, but the judgement, which was published last year, noted the ongoing investigation "cast a shadow over Soma's business and gave rise to a risk of insolvency".
Both the SFO and Soma declined to comment on the costs of the investigation.