Tanzania's chief auditor said on Monday the Tanzania Revenue Authority (TRA) failed to collect about four billion U.S. dollars revenue in the 2014/15 financial year due to "inefficiency" and "negligence".

Mussa Assad, Tazania's Controller and Auditor General, blamed the TRA's failure to meet its revenue targets in 2014/15 partly on its failure to collect "all due taxes" from registered tax payers.

In his 2014/2015 audit report for the central government, Assad said the bulk of the uncollected amount -- about 3.4 billion dollars -- were pending in tax appeals bodies.

"My audit this year noted that TRA had long outstanding cases at various tax appeals machinery," said Assad in the report.

Meanwhile, Assad cautioned the government over the increasing domestic borrowing, saying it was "bad for the economy" and had increased the cost of living.

Tanzania's internal borrowing -- which is mainly for budget and rollovers -- reached nearly two billion dollars during the 2014/2015 financial year, about 0.5 billion more than approved estimates, according to the report.